Modal Verbs IV

Some modal verbs (must, cannot, may, might, could) can have more than one use. 

When we want to talk about the degree of possibility of something, we use them. Depending on how sure we are about the fact, we will use one modal verb or another. Besides, depending on whether our prediction was in the past or in the present, we will change the verb tense. 

Here is a quick guide on how to use them:

• Modal verbs in present tense: Modal verb + inf
• Modal verbs in past tense: Modal verb + have + past participle

Must

• Present: we believe that something is true.

You have been studying the whole morning. You must be tired.

• Past tense: we believe that something is true.

He studied a lot for his exams. He must have been happy after he finished them.

Cannot (can’t)

• Present: We are certain that something is NOT possible.

I saw him on the city center ten minutes ago so he cannot be home yet.

• Past: We are certain that something is NOT possible.

You cannot have seen him in the office, he is on a trip.

 

May / Might / Could

• Present: You think that something is possible.

I might go to the cinema, I don’t know yet.

• Past: you think that something is possible.

He might have forgotten to call you. (He did not call, so there is a possibility that he forgot).

 

Ex.