Modal Verbs

modal verb with a main verb to express ability, obligation,etc.
After modal verbs, we use the infinitive without to: I can speak English.
Modal verbs don’t add –s after he/she/it: He can drive.
In questions and negative sentences, we don’t use the auxiliary do: May I come in?
Modal verbs don’t have past, perfect or future forms, or participle forms. We use other verbs instead: They had to leave early yesterday. We haven’t been able to find a suitable accommodation.
These verbs and expressions have similar meanings to modal verbs: be able to, manage to, have(got) to, need to, be allowed to and ought to.