Grammar: Expressions For Modal Auxiliaries
CAN: be able to + verb
She will be able to do it tomorrow.
They were not able to come.
Will you be able to bring it next week?
MUST: have to + verb
We will not have to go there.
I had to buy new curtains.
Did you have to go there?
MAY: be allowed to + verb
We are allowed to stay out until 8 p.m.
Will we be allowed to go to the cinema?
They were not allowed to buy anything.
These expressions can be also used in the present tense.
I am able to win the tournament.
Is he allowed to buy a dog?
You have to send the letter today.