Модальные глаголы, сводная таблица

Modal verb

Present

Past

Must can be used in affirmative sentences. In questions and negatives the forms can and can’t are used.

Must - is used in situations where the speaker is sure about smth, because it’s logically necessary. (100 % of certainty).

Positive

Negative

Positive

Negative

Must

Can’t

Must have V₃

Can’t /couldn’t have V₃

Everyone is wearing a jacket.

It must be cold. 

That can’t be the postman – it’s only 7 a.m.

We went to Majorca. That must have been nice.

It can't have been David.(I'm sure it wasn't David.)It couldn't have been David.

May – is used to talk about one kind of possibility: the possibility (chance) that smth will happen, or is happening. (less than 50% certainty").

May

May not

May have V₃

May not have V₃

May is formal and is often found in writing.

1)Where are my keys?They may be in the car.

2)I may go to the party tonight.

She may not be at home. (It’s possible that she isn’t at home.

Polly’s very late. She may have missed her train.

She may not have known his address.

Might - is not the past of may; it suggests a smaller (present or future) probability than may.(less than 50% certainty").

Might

Might not

Might have V₃

Might not have V₃

Might is less formal than may, and is more common in conversation.

I might get a job soon. Yes, and pigs might fly.

He might not come back soon.

1)shows that something probably is not true.

2)shows that something probably will not happen 
in the future.

What do you think that noise was? It might have been a cat. + to say that a past event was possible, but didn’t happen: You were stupid to try climbing up there. You might have killed yourself.

He might not have come back yet.

Could – is used to express possibility which is one of many. This form isn’t as strong as might or may. It’s just one of a number of possibilities.

Could

Could not

Could have V₃

Could not have V₃

It could be John, but I can't see clearly.

Anton couldn't be lying to us, he is an honest man. = impossibility

It couldn't be true!

It could have been John, but I'm not sure.

It couldn't have been Tom. Tom was in Chicago last week. = impossibility;