MODALS OF DEDUCTION: MUST, CAN´T, MIGHT/MAY/COULD

Modal verbs are auxiliary verbs that can not function as a main verb, a difference of the auxiliary verbs "to be", "to do" and "to have" that can function as a main verb.


Modal verbs express modality, ability, possibility, need or other condition. We use them for the future and the conditional.




FORM
                                                                           Subject + modal + Base form




FUNCTION 

CAN'T
We use can't to say that it's impossible that something is true.



MUST
We use must to say that we are sure that something is true.

MIGHT/COULD/MAY

We use might could may to say that something is possibly true.

                                                                EXAMPLES                                                                                             - That woman can't be Sally. She's blond and Sally has dark hair.                                                 - It must be after 8 p.m.  Look! It's dark outside.                                                                       - There might be a storm later.  The sky is very cloudy.