Can, could, may, might, must, shall, should, will and would are the modal verbs.
They always go together with the infinitive of the main verb, for example:
I must go.
You should call him.
John can meet me at the airport.
What is the difference between modal verbs and other verbs?
The modal verbs are different from other verbs:
- they do not have the ending -s with he, she, it
My daughter is four years old and she can read and write.
Mr Johnson might come tomorrow.
- they do not require an auxiliary verb (be, do, have)
Can you close the window, please? BUT
Does he always close this window?
- they do not have past (except "could") and future forms
I must go to the dentist. BUT
I had to go to the dentist yesterday.
- we do not put "to" before the second (main) verb
We may sit here. BUT
I want to sit here.
- they don't have infinitive forms, they can't be used after "to" or another modal verb
A candidate should be able to list the pros and cons of functional programming. WRONG A candidate should can...
Meaning of the basic modal verbs and "have to" in a table
|may/might||may not/might not||
|have to||not have to||
Expressing probability with modal verbs
We can use modal verbs when we want to make a proposition about something. We choose the verb depending on how certain we are.
|can't||I'm sure it is not true||It can't be true. I don't believe it.|
|could||possibly, maybe||She could be on the train to Paris now.|
|might||I might join you later.|
|must||I'm sure it is true||It must be a mistake!|
|will||it is certain||She will be at home by now.|
When we express probability with modal verbs, we can use more constructions than just "a modal verb + infinitive".
- modal verb + be + -ing
In fact, it is the infinitive of the present continuous form (to be joking, to be leaving, to be talking).
She might be having lunch.
This can't be happening again!
You must be joking.
- modal verb + have + past participle
When we make a guess or express regrets about the past situation, we use a past modal verb.
He must have gone out.
I should have listened to you.
Jessica didn't invite me, but I couldn't have come anyway.