THE FORM OF MODAL AUXIALIARIES
The verbs is the list below are called modal auxiliaries. The are helping verbs that express a wide range of meanings (ability, permission, possibility, necessity, etc). Most of the modals have more that one meaning.
AUXILIARY + THE SIMPLE FORM OF A VERB
can (a) I can speak English.
could (b) He couldn’t come to class.
may (c) It may rain tomorrow.
might (d) It might rain tomorrow.
should (e) Mary should study harder.
had better (f) I had better study hard.
must (g) You must see a doctor today.
will (h) I will be in class tomorrow.
would (i) Would you please close the door?
Can, could, may, might, should, had better, must, will, and would are followed by the simple form of a verb.
They are not follwed by to:
CORRECT : I can speak English.
INCORRECT: I can to speak English.
The main verb never has a final -s.
CORRECT : Olga can speak English.
INCORRECT: Olga can speaks English.
AUXILIARY + TO + THE SIMPLE FORM OF A VERB
have to (j) I have to study tonight.
have got to (k) I have got to study tonight.
ought to (l) Kate ought to study harder.
Have, have got, and ought are followed by an infinitive (to + the simple form of a verb).