Modal verbs in English are a class of auxiliary verbs used mostly to express modality. We use modal verbs to show if we believe something is certain, probable or possible (or not). We also use modals to do things like talking about ability, asking permission, making requests and offers, and so on.

The principal English modal verbs are can, could, may, might, must, shall, should, will and would

Certain other verbs (semi-modals) are sometimes, but not always, classed as modals: ought, had better, dare and need.

Modal verbs have only one form. They have no to-infinitive form, -ing form, past form or -ed form.

Modal verbs do not change form for tense or person. 

Modal verbs cannot be used with another modal verb.

Modal verbs always go before other verbs in a verb phrase.

Affirmative forms: modal verbs are placed first in the verb phrase (after the subject) and are followed by a verb in the base form. 

He ought to help his friend.

Negative forms: negatives are formed by adding ‘not’ after the modal verbs. We don’t use don’t/doesn’t/didn’t with modal verbs:

You must not smoke here.

Question forms: the subject and the modal verb change position to form questions. We don’t use do/does/did:

May I come in?

We use modal verbs in question tags:

He can't do it himself, can he?

As noted above, English modal verbs do not have infinitive, participle, and in some cases past forms. However in many cases there exist equivalent expressions that carry the same meaning as the modal, and can be used to supply the missing forms. 

The modals can and could, in their meanings expressing ability, can be replaced by am/is/are able to and was/were able to. Additional forms: the infinitive (to) be able to, and the participles being able to and been able to.

The modals may and might, in their meanings expressing permission, can be replaced by am/is/are allowed to and was/were allowed to.

The modal must in most meanings can be replaced by have/has to, had to, to have to, having to.

When will or shall expresses the future, the expression am/is/are going to (was/were going to, (to) be going to, being/been going to) has similar meaning. 

The modals should and ought to might be replaced by am/is/are supposed to (was/were supposed to, (to) be supposed to, being/been supposed to).


Can and Could 

Can expresses possibility: ability, permissibility, or possible circumstance.

Possibility: we use the modal can to make general statements about what is possible.

It can be hot in summer.

We use could as the past tense of can.

It could be very hot in summer.

Ability: we use can to talk about someone’s skill or general abilities.

I can speak English.

Permission: we use can to give permission.

You can smoke here.

We use can to ask for permission to do something

Can I smoke here?

Could is more formal and polite than can.

Instructions and requests: We use could you and as a polite way of telling or asking someone to do something.

Could you make a cup of coffee, please.

Can is less polite:

Can you make a cup of coffee, please.

Possible circumstance:

There can be strong rivalry between siblings.

Offers and invitations:

How can I help you?

I can help you.


We use the negative can’t or cannot to show that something is impossible:

That can’t be true.


May and might

The verb may/might expresses (future) possibility when we are not sure about something: 

I might see you tomorrow.

It might rain later.

I may be away at 12 PM / I might be away at 12 PM

We use may if we want to make polite requests:

May I borrow your pen? 

As the past tense of may for requests or for very polite requests we use might:

She asked if she might borrow my pen.

Might I ask you a question?

We use may if we want to give permission or to ask permission.

You may take only one book.

May I sit next to you?

May not can be used to not give permission or to prohibit someone from doing something.

You may not smoke here.

Speculate about past actions (may + have + past participle)

He may have gone home. He might have gone home.

To express wishes

May God bless you!



Must is used to express obligation, duty or strong intention (this also refers to laws and regulations):

Luggage must not be left unattended.

I must phone my sister.

Used to emphasize the necessity of something.

I must get some sleep.

Used to expresses logical assumptions, used to show that something is very likely, probable, or certain to be true (must + have + past participle)

There's no food left - we must have eaten it all. 

Used for emphasis

I must say, I’m not very impressed.


Will and Would

Used to talk about what is going to happen in the future, especially things that you are certain about or things that are planned:

I will be 25 years old next month.

Used to talk about what people want to do or are willing to do:

I'll see you tomorrow.

I'll be late.

We use will to make offers and promises, to invite or ask someone to do something:

Will you join us for a cup of coffee?

Used in conditional sentences with "if":

If you don't water plants, they'll die.

Used when referring to something that always or usually happens:

Accidents will happen.

Used to express strong probability with present time reference:

That will be Kate at the door.

Used to give an order:

You will do it right now.

We use would as the past tense of will.

Used to refer to future time from the point of view of the past:

She said she would visit us tomorrow.

Used to refer back to a time in the past from a point of view in the future:

He tried to persuade me but I would not listen to him.

Used to refer to a situation that you can imagine happening:

I would hate to miss the concert.

Used with "if" in conditional sentences:

He would go there if he had time.

Used in polite requests and offers:

Would you mind passing me the salt?

Used to show that you prefer to have or do one thing more than another:

I’d prefer to eat at home rather than go out.

I'd rather eat at home.

Used to talk about things in the past that happened often or always:

I would always eat early and would walk to school.


Shall and Should

Shall is used instead of "will" when the subject is "I" or "we":

Shall I see you tomorrow?

I shall have no lessons tomorrow.

Shall is used, with "I" or "we", to make a suggestion:

Shall I close the window?

Shall I read?

Shall is used to say that something certainly will or must happen, or that you are determined that something will happen:

Don't worry, I shall be there to meet the train.

Should is used to say or ask what is the correct or best thing to do:

You should start eating better.

You should never lie.

Used to show when something is likely or expected:

Kate should be in London by now.

Used to speak about obligation:

I should be at work before 9:00.

Should is used after "for fear that", "in case":

He took his umbrella in case it should rain.

Used after "why" when giving or asking the reason for something:

Why should anyone want to eat something so horrible?

Used after "I" when giving advice:

I shouldn't worry about it if I were you.

Should is sometimes used as a first-person equivalent for would (in its conditional, "future-in-the-past" uses and reported speech):

I asked him where I should wait for him.

I said that I should be glad to see him.

If they should come, I shall speak to them.


Dare, need, had better, ought to and used to (semi-modal verbs)

Dare, need, had better, ought to and used to are often called semi-modal because in some ways they are formed like modal verbs and in some ways they are like other main verbs.

Like modal verbs, ought to and used to do not change form for person. Needn’t and daren’t do not have a third person -s in the present:

It used to be so easy. 

He ought to help his friend.

He needn’t hurry.

Kate daren’t tell Sue the truth.

Like main verbs, the negative form of need, dare and used to is made by using do. But it can also be made without using do (like modal verbs).

You don’t need to come so early.

You needn’t come so early.

I don’t dare (to) tell them the truth.

I daren’t tell them the truth.

The negative form of ought to is not made with do:

He oughtn’t to help his friend.

Like main verbs, the question form for need, dare and used to is made by using do:

Does he need my help?

Did you use to play rugby when you were younger?

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