Modal Verbs

Modal verbs are used to show the speaker’s attitude towards the action. We use them with other verbs. Modal verbs are not “complete” verbs. They are called defective because they lack (except dare and need) component tenses, the passive voice and have some other peculiarities:We can’t use them as “to”-infinitives: to go, to speak;We don’t use the “to”-infinitives after modals (You mustn’t phone now. It’s late);There is no -(e)s in the 3rd person singular (The boss can see you now).

Can

If we mean that someone managed to do something in the particular situation, you have to use was/were able to do smth (not could).

Mental, physical, circumstantial ability

Can you lift this box?

He can solve the most difficult problems.

They can get there by bus.

Permission

You can go now.

You can play with the boys there.

Request

Can you do me a favour?

Could you get me a glass of water?

Prohibition

You can't cross the street here.

You can't smoke in here.

Strong doubt

You can't have done it!

She can't be still waiting for you!

Astonishment

Can he be working now?

Can he have been waiting for us all this time?

Need

Need expresses necessity. It is mostly used in negative and interrogative sentences.

Absence of necessity

She needn’t get up early.
The lessons begin at ten.
(Можно не ...)

Something that
has been done, was unnecessary

The water was clean.
You needn’t have boiled it.
(Можно было и не ... ;
зря; напрасно)

To be to

We use "to be to" when we talk about an agreement or arrangement or a strict order.

An agreement or arrangement,
part of a plan
(должен)

We were to meet at the entrance to the theatre at
a quarter to nine.

They are to go to Spain in July.

A strict order/prohibition
(побудительное предложение)

You are to go straight to your room.

You are not to get your feet wet.

Something thought
as unavoidable
(предстоит, суждено)

Sally wanted Morris to be friendly with her,
but evidently it was not to be.

He went about thinking of his life
and what was to become of him.

May

There is no important difference between may and might in this meaning. Sometimes “might” expresses greater uncertainty than “may”.

To ask permission/give permission (можно)

May I borrow your umbrella, please?

May I see your garden, please?

To talk about possible happenings in the Future (возможно, может быть)

I’m not sure where to go for my holiday.
I may go to Italy. (= perhaps I will go)

The weather forecast is not very good.
It might rain this afternoon. (= perhaps it will rain)

To talk about possible plans (могу, возможно)

I am going to Italy in July. (For sure)

I may/might go to Italy in July, (it’s possible)

Reproach (only might)
(мог бы)

You are becoming forgetful.

You might have reminded me about it.

Uncertainty, supposition implying strong doubt

He may be in his office now.

He may not have noticed you in that crowd.

You might have been sleeping.

Should and ought

There is hardly any difference between these verbs, very often they are interchangeable. There is a difference in construction: ought is always followed by the to-infinitive. Moral obligation or duty is more often expressed by ought to. It is a little stronger than should.

Moral obligation

A man should help his parents
when they become old.

Advice

You should be more careful.

Disapproval

You shouldn’t treat me like this.

Criticism of the past action

She was feeling unwell yesterday,
she shouldn’t have gone to her office.

Reproach

You can’t remember what I said,
you should have listened more carefully.

Regret

It was his birthday yesterday.
I should have sent him a birthday card.

To have to

We use do/does/did with “have to” in present and past questions and negative sentences.

Obligation or necessity arising
out of circumstances
(должен = приходится,
вынужден)

I have to get up at 6 every day.
My working day out of circumstances begins at 8.

Last night Den suddenly became ill.
We had to call the doctor.

Must

We can only use “must” to talk about the present and future.

Obligation, necessity
(=have to...) (должен)

Well, it’s 10 o’clock, I must/have to go now.

A command, an urgent request
(побудительное предложение)

You must leave the room at once.

Prohibition
(нельзя, запрещается)

You mustn’t speak to a prisoner in a foreign language.

Probability or supposition
bordering on assurance, almost a conviction

He must be at home at this hour.

He must be writing about his travels.

He must have taken a lot of photos
while he was on the islands.