Introduction to modal verbs

Some facts about modal auxiliary verbs:

1.     They do not have an infinitive form. 

can             

to can      

2.     We use them before other verbs to give more information. We use the bare infinitive of the main verb.   We do not use 'to' after a modal.

I can swim.     

I can to swim.  

3.     We use 'not' for the negative form

I can't swim.       

I don't can swim.

and we do not use 'do' in questions.

Can you swim?     

Do you can swim?   

4.     Modals have only one form.

I can

You can

He/she/it can

We can

They can 

Can

Could

May

Might

Must

Shall

Should

Will

Would 

Modal auxiliary verbs have different meanings. This table shows some common uses.

See the rules on each modal for more detailed information.