TOIEC Grammar - Modal Verbs

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Modal verbs

1. Definition of a modal verb

A modal verb is:

an auxiliary verb

used to express intention, necessity, obligation, offer, permission, possibility, prohibition, question,

request, suggestion

cannot function as a main verb in a sentence

2. Use of model verbs

2.1. Can

- To talk about theoretical possibility (khả năng có thể xảy ra nói về mặt lý thuyết) - to say that

situations and events are possible theoretically.

Glass can be blown. (It is theoretically possible to blow glass.)

Wars can break out any time. (It is theoretically possible for wars to break out any time.)

Smoking can cause cancer.

Noise can be quite a problem when you are living in a city.

Do not use can to talk about future probability (điều có thể xảy ra ở tương lai) – to say that something will

happen in future. We express this idea with may or might.

It may rain this evening. (NOT It can rain …)

There may be a strike next week. (NOT There can be a strike …)

I may get a job soon.

Might expresses a less definite possibility than may. Could is also used in the same sense.

It could rain this evening. (= It might rain this evening.)

- To talk about possibility

Can is often used in questions and negatives to talk about the logical possibility that something is true.

There is the doorbell? Who can it be?

We use could, may or might in affirmative clauses, not can.

Where is John? He could/may/might be in the garden. (NOT He can be in the garden.)


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- To talk about ability

We can use can to talk about present or general ability – to say that we are capable of doing something.

I can speak 10 languages.

She can cook well.

Can you knit?

If you are not satisfied with this product, you can send it back.

or talk about ability during a specific event

With a burst of adrenaline, people can pick up cars.

Note that be able to can often be used with similar meanings.

He is able to support her. (= He can support her.)

They were able to catch the thief. (= They could catch the thief.)

We do not use can to talk about future ability. Instead, we use will be able to or other words.

Someday scientists will be able to find a cure for cancer. (NOT Someday scientists will can find a cure

for cancer.)

- To ask for or give permission

Can is sometimes used to ask for and give permission (sự cho phép). Some people, however, think that may

is more correct than can.

I can drive Susan's car when she is out of town.

You can go out and play after you have finished your homework.

You can park on either side of the road here.

Can I go to the movies, mom?

Note that we can also use could to ask for permission. It is a more polite form of can.

Could I speak to Mr. John, please?

Could I have look at your newspaper?

Cannot is used to refuse permission.

Can I go to the movies, mom? No, you can’t.


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- To make requests and offers

Can is used in polite requests (yêu cầu lịch sự) and offers of help (đề nghị giúp đỡ).

Can you give me a lift to school?

Can you get me a cup of coffee?

Can I help you with those bags?

Note that Could is a more polite way of making requests and offers.

Could you help me with my homework?

Could you lend me some money?

2.2. Could

- To talk about past ability in general

Could is often used to say that somebody was able to do something in the past. However, Could refers to the

past only when the context makes the time clear.

My father could walk without help when he was 95.

When we were children, we could watch TV whenever we wanted to.

Could not (also couldn't) shows past inability.

She spoke in such a low voice that most of us could not hear her.

We found that we couldn't depend on our guide.

Could is used to talk about past ability in general. We do not normally use could to say that somebody

managed to do something on one occasion. But with certain verbs like see, hear, taste, feel, smell,

understand, remember etc., could can be used for particular occasions (các sự kiện cụ thể) as well.

Suddenly I could hear a loud noise.

I could smell something burning.

- As the past equivalent of can

Could is the past equivalent (quá khứ tương ứng) of can in indirect speech.

He said, "I can drive." He said that he could drive.

She said, "I can't climb up the hill." She said that she could not climb up the hill.

- To make polite requests or offers


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Could is often used to make a request or offer sound more polite.

Could I have a glass of water, please?

Could you help me with these bags?

- To express possibility or uncertainty

You could get a better job if you spoke English. (=You would be able to get a better job if you spoke

English.)

You could do it if you tried hard. (=You would be able to do it…)

If only I had some working capital, I could start a new business. (=…I would be able to start a new

business.)

Note: The structure could have + past participle can be used to criticize people for not doing things. It can

also be used to talk about past events that did not happen.

I have been waiting since morning - you could have said that you weren't coming.

Why did you drive so carelessly? You could have killed yourself.

2.3. May


May is used to talk about the chances of something happening.

I think it is going to rain. You may be right.

There may be a strike next week.

Where is John? He may be out shopping.

May well is used to suggest a strong possibility.

I think it is going to rain. You may well be right.

May is not normally used in direct questions about probability.

Are they likely to help us? (BUT NOT May they help us?)

But note that may is possible in indirect questions about probability.

May we not be making a big mistake?

May + perfect infinitive

The structure may + perfect Infinitive (have + past participle) can be used to say that it is possible that

something happened or was true in the past.


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Alice is very late. She may have missed her train. (= It is possible that she missed her train.)

May + perfect infinitive can also refer to the present or future.

I will try phoning him, but he may have gone out by now.

- To ask for permission

May can be used to ask for permission. It is more formal than can and could.

May I come in?

May is used to give permission; may not is used to refuse permission and to forbid.

May I come in? Yes, you may.

May I have a look at your papers? No, I am afraid you may not.

Must not is also used to forbid (ngăn cấm). It is stronger than may not.

Students must not use the staff car park.

May and might are not normally used to talk about permission which has already been given or refused, about

freedom which people already have, or about rules and laws. Instead, we use can, could or be allowed.

Can you/Are you allowed to park on both sides of the road here? (More natural than May you allowed

…)

When we were children, we could watch TV whenever we wanted to. (NOT .. we might watch TV …)

- May in wishes and hopes

May is used in formal expressions of wishes and hopes. May often comes at the beginning of the sentence.

May God bless you!

May you both be very happy!

May the devil take him!

May you prosper in all that you do!

Note:

1. May and Can:

Both can and may can be used to talk about possibility. But there is some difference between them.

Can is used to talk about theoretical possibility.

May is used to talk about factual possibility.


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Compare:

The road may be blocked due to the procession. (Factual possibility.)

Any road can be blocked. (Theoretical possibility - It is possible to block any road.)

There may be a strike next week. (It is possible that there will be a strike next week.)

Strikes can happen any time. (It is possible for strikes to happen any time.)

If you drive carelessly, you may have an accident. (Factual possibility)

Accidents can happen any time. (Theoretical possibility)

When we talk about possibility, could often means the same as may or might.

You may/might/could be right.

2. May not and Cannot

May not suggests improbability.

Cannot suggests impossibility.

Compare:

We may not go camping this summer. (= It is possible that we may not go camping.)

We cannot go camping this summer. (= It is not possible for us to go camping this summer.)

2.4. Might


We often use might to say that there is a chance that something is happening, or that there is a possibility of it

happening.

It might rain this evening.

She might come.

Might + perfect infinitive

The structure might + perfect infinitive can be used to say that it is possible that something happened or was

true in the past.

What was that noise? It might have been a cat.

The same structure can be used to say that something was possible but did not happen.

You were stupid to try climbing up there. You might have killed yourself.


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- To ask for and give permission

Might can be used to ask for permission. It is very polite and formal; it is not common and is mostly used in

indirect questions.

May I put the TV on?

I wonder if I might borrow your car.

“May I borrow the car?” “No, I’m afraid you may not”

Note:

May and Might

Might is the past equivalent of may in indirect speech. But it does not normally have a past meaning. It is used

in the same way as may to talk about the present or future. The difference is that might usually refers to

situations that are less probable or less definite. It is used when people think that something is possible but not

very likely.

I may get a job soon. (Perhaps a 50% chance)

I might get a job soon. (Perhaps a 30% chance)

Might can mean ‘would perhaps’.

Don’t play with knives. You might get hurt. (= Perhaps you would get hurt.)

2.5. Will

- To express simple futurity

Will is used to talk about future events that you are certain about or things that are planned.

There will be trouble if he catches you stealing his flowers.

The train leaves at 9:30, so we will be home by lunchtime.

- To talk about willingness

Will shows determination or willingness (sự sẵn lòng) on the part of the speaker.

I will come with you.

There is the doorbell. I will go.

We will not surrender.

Will can also express a promise or a threat.

I will do whatever I can to help you.


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I will teach him a lesson.

We will dismiss you from service.

- To ask someone to do something

Will can be used to ask someone to do something.

Ask John if he will help.

Will you lend me some money?

Will you give the book to John when you meet him?

- To make requests and offers

Will can be used as a polite way of inviting someone to do something or of offering someone something. Note

that would is a more polite form of will.

Will you join us for a drink?

Will you send me the report?

Won’t you is used to make a pressing offer.

You will have some coffee, won't you?

- To give orders

Will you be quiet?

If you don't behave, you will go straight to bed.

2.6. Would

- To make polite offers and requests

Would is often used in polite requests and offers. It is a softer, less definite form of will.

Would you mind moving a bit?

Would you mind sharing a room?

I would like to meet the manager.

Would can also be used to express an opinion in a more polite way without being forceful.

This is not what we would expect from a professional service.

- To talk about past habits

Would can be used to talk about past events that happened often or always.


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He would always bring us nice gifts without telling why.

The old man would recline in a corner and sleep most of the time.

After dinner we would sit in a common room and chat for a while.

Would is often used to suggest that what happens is expected because it is typical, especially of a person's

behaviour.

She would always trust the wrong the person.

'Ann rang to say that she was too busy to come.' 'She would - she always has an excuse.'

- To talk about willingness and determination

Would can express willingness or a rather perverse determination.

He said he would try his best to help me. (Willingness)

He would bet on that horse, though I asked him not to. (Determination)

She would have her own way.

Wouldn't shows unwillingness.

I asked him to move his car, but he said he wouldn't.

- To talk about imaginary situations

Would is sometimes used to refer to a situation that you can imagine happening.

I would hate to miss the show.

I would go myself but I am too busy.

It would have been quite boring to sit through the entire speech.

Note:

1. Would and used to

Both would and used to can refer to repeated actions and events in the past.

She would/used to always carry an umbrella.

Note that used to can refer to past states; would cannot.

I used to have an old Rolls Royce. (NOT I would have …)

2. Would rather

Would rather expresses choice or preference.


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She would rather die than marry him.

They would rather go to jail than pay the fine.

3. Would and Will

Would is a softer, less definite form of will. It is used in polite requests and offers.

I would like to meet him.

Would can act as the past of will in indirect speech.

She said, ‘I will not live here anymore.’

She said that she would not live there anymore.

2.7. Shall

- With the first person

In the first person shall expresses simple futurity. It is used to show the strong possibility or near certainty of an

action or event which is to take place in the future.

- With the second or third person

In the second and third persons shall may express a command.

You shall go at once. (= You are commanded to go at once.)

He shall carry out my instructions. (= He is commanded to carry out my instructions.)

Sometimes it is used to make a promise.

He shall be given a present if he passes this year.

Shall may also express a threat.

You shall regret this.

They shall pay for this in due course.

Note that shall is becoming increasingly less common in Modern English. Instead of using shall in the second

and third person to indicate a command, promise or threat, people often use other verbs and expressions.

For: You shall go at once people often say

You will have to go at once

You are to go at once

You must go at once.


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Usage

- To make suggestions

Shall can be used with the first person pronouns (I or we) to make suggestions.

You don't look well. Shall I call the doctor?

It is very cold. Shall I close the window?

Shall I drop you at the station?

- To talk about certainty

Shall can show certainty. It is used to say that something will certainly happen, or that you are determined that

something will happen.

Don't worry. I shall be there to help you.

She shall clean the kitchen, no matter whether she likes it or not.

2.8. Should

- To express obligation

Should is often used to talk about duty (trách nhiệm, bổ phận) or obligation (nghĩa vụ). It can also be used to

say or ask what the correct or best thing to do is.

You should tell the truth.

If you are not feeling well, you should consult a doctor.

There should be an investigation into the cause of the accident.

Note that should is not as strong as must.

In questions, should is used to ask for advice or instructions.

It is rather cold here. Should I turn the heating on?

What should we do now?

Should I seek his opinion?

Should we talk to him?

- To express probability

You should find this grammar book helpful.

He should be here soon – he left home at six.


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‘Granny will be staying with us for a couple of months.’ ‘That should be nice.’

Mount Everest should be visible from Tiger Hill if the sky is clear.

Should have + past participle

The structure should have + past participle can be used to talk about past events which did not happen.

I should have sent the money this morning, but I forgot.

This structure can also be used to talk about past events which may or may not have happened.

They should have reached home by now. It is 10 o’clock.

We can use should not have + past participle to refer to unwanted or unnecessary things that happened.

You shouldn’t have said things like that to her.

It is very kind of you, but you shouldn’t have bothered.

Note:

1. Should or Would?

In British English, both would and should can be used after first person pronouns (I and we). There is no

difference in meaning.

I would/should like some sweets before I go to bed.

We would/should be happy to receive them at the airport.

2. Should after why

Should can be used after why to suggest surprise.

Why should anyone want to buy something so useless?

Why shouldn’t she buy it if she can afford it?

I don’t see why we should have to pay for your mistakes.

3. Should in subordinate clauses (mệnh đề phụ)

Should can be used after certain adjectives expressing personal judgments and reactions. Examples are: odd,

strange, sad, unfair etc.

It is strange that she should find old men attractive.

It is odd that she should want to trust him again.

It is unfair that she should have died so young.


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This also happens after adjectives and nouns expressing the importance of an action. Examples are:

necessary, important, essential, vital, eager etc.

It is important that the meeting should be a success.

It is necessary that she should be told.

Should can used after so that, in order that, for fear that, in case and lest to show the purpose of an action.

He took an umbrella so that he shouldn’t get wet.

He ran lest he should miss the train.

He took his umbrella in case it should rain.

4. Should in conditional clauses

Should is used in conditional clauses expressing possibilities, suppositions etc.

If he should come, ask him to wait.

Should it rain, there will be no picnic today.

Note that if he should come indicates less likelihood of his coming than if he comes. The sentence means

something like this: There is not much chance of his coming. But if he turns up, ask him to wait.

2.9. Have to

- To express certainty

That must not be Jerry. They said he has blond hair, not red hair.

- To talk about necessity

She has to read four books for this literature class.

- To show obligation

They have to leave early.

2.10. Must

Must indicates that it is necessary or very important that something happens. If you say that you must do

something, you mean that you have a definite intention to do something in future.

I must get my hair cut.

I must stop smoking.

We must get someone to repair the roof.

If you tell someone else that they must do something, you are emphasizing that it is a good idea for them to do

that.


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You must stop lying.

Usage

- To express a conclusion (kết luận)

Must can be used to express the conclusion that something is certain or highly possible.

If A is bigger than B, and B is bigger than C, then A must be bigger than C.

There is the doorbell. That must be the postman.

- Must in questions and negatives

In questions we use can to express certainty, not must.

Somebody is knocking at the door. Who can it be? (NOT Who must it be?)

In negative clauses we generally use cannot/can’t to say that something is certainly not the case.

It can’t be your mother. She is in New York.

However, mustn’t is normal in question tags.

It must be nice to be a bird, mustn’t it?

- To express necessity

Must is often used in affirmative sentences (câu khẩng định) to say what is necessary, and to give strong

advice and orders to ourselves and other people.

We must get up early and start on our way.

We must build a strong army to defend the country.

I must stop smoking.

Must can be used in questions to ask about what the hearer thinks is necessary.

Must I go now?

In American English, have to is more common.

Do I have to go now?

Must not or mustn’t is used to say that things should not be done, or tell people not to do things.

You must not open this parcel until Christmas day.

You must not lie.


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Note: Must and Have to

Both must and have to can be used to express the conclusion that something is certain. Note that have to is

more common in American English.

He must be mad to do this. (OR He has to be mad to do this.)

You must be joking. (You have got to be joking.)

Conclusions about the past are usually expressed with must followed by the perfect infinitive (have + past

participle).

I hear you have been to Australia. That must have been interesting.

- Necessity

Must and have to can both be used to talk about necessity. In American English, have to is more common.

We must/have to build up a strong army to defend the country.

- Obligation

Both must and have to can be used to talk about obligation.

In American English have to is the normal form.

British English often makes a distinction between them.

Must is used mostly to talk about the feelings and wishes of the speaker and hearer.

Have (got) to is used mostly to talk about obligations that come from ‘outside’ – for example from

laws, regulations, agreements and other people’s orders.

Compare:

I must stop smoking. (= I want to stop smoking.)

I have to stop smoking. (= Doctor has asked me to stop smoking.)

You really must go to church next Sunday. (I am telling you to.)

Catholics have to go to church on Sundays. (Their religion tells them to.)

Will have to is used to talk about future obligation, but have (got) to is preferred when arrangements for the

future have already been made.

When you leave school you will have to find a job. (Future obligation)

I have got to go for a job interview tomorrow. (It is already arranged.)


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Had to is used to talk about past obligation. Must is used with the perfect infinitive (have + past participle) to

express certainty about the past.

Mary isn’t in her office. She had to go home. (= It was necessary for her to go home.)

Mary isn’t in her office. She must have gone home. (= It seems certain that she has gone home.)

Must not and do not have to/ have not got to have quite different meanings. Must not is used to tell people not

to do things; do not have to/ have not got to is used to say that there is no obligation.

You must not tell him. (= Don’t tell him.)

You don’t have to tell him. (= You can if you like but it is not necessary.)

2.11. Ought to

Ought is different from other auxiliary verbs. It is used with to

We ought to respect our parents.

We ought to help the poor.

Note that to is dropped in question tags.

You ought to love your country, ought not you? (NOT…ought not you to.)

Ought is rarely used in questions and negatives; should is generally used instead. A structure with think …

ought is also common.

We ought to help them, shouldn’t we? (More natural than ought not we?)

Do you think I ought to consult a doctor? (More natural than Ought I to consult a doctor?)

Should we tell her? (Less formal than Ought we to tell her?)

Meaning

Ought to expresses duty, necessity, desirability and similar ideas. It is often used to advise people – to tell

them that they have a duty to do things. The meaning is similar to should

You ought to attend office regularly. (Duty)

We ought to help the needy. (Moral obligation)

We ought to buy some furniture. (Necessity)

Note: Ought is not as forceful as must.

Ought to have + past participle

When ought refers to past time, it is followed by the perfect infinitive. This structure can be used to talk about

things which were supposed to happen but did not.

I ought to have written to my parents, but I forgot.

You ought to have invited her to your party.


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This structure can also be used to make guesses.

It is ten o’clock. He ought to have reached home.

Ought not to have can be used to talk about things that happened unnecessarily.

We ought not to have wasted so much time over it.

We have done things that we ought not to have done.

We have left undone things that we ought to have done.

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TOIEC Grammar - Modal Verbs