Modals

Modals verbs are verbs frequently used to express hability, necessity, possibility, probability, permission,  obligation, duty and others.

The main aspect of these verbs is that they do not change. The second important characteristic of modals verbs is that after them, verbs do not change. It is used only the original form (infinitive).

Here there are some examples of their use.

Hability (can)

I can play guitar. I can't play guitar. Can I play guitar?

Necessity (need to)

I need to get money.

Possibility (may)

He may get angry, if he know the truth.

Duty

The soldiers must defend the homeland.