Modals

The modal verbs include can, must, may, might, will, would, should. They are used with other verbs to express ability, obligation, possibility, and so on.

Can

To express ability:

• I can speak a little Russian.

To request permission 

• Can I open the window?

May

To express possibility 

• I may be home late.

To request permission 

• May I sit down, please?

Must

To express obligation 

• I must go now.

To express strong belief 

• She must be over 90 years old.

Should

To give advice 

• You should stop smoking.

Would

To request or offer

• Would you like a cup of tea?

In if-sentences

• If I were you, I would say sorry.

Will

Assuption

• They will be here in a minute.

Won't

Refusal

• I won't stop until I get what I want.

Migth as well

The last option, when the speaker is not enthusiastic.

• We migth as well just pay the bill.

Is supposed to:

Obligation

• They were supposed to deliver the package this morning.

Modals are auxiliary verbs. They do not need an additional auxiliary in negatives or questions.