These three verbs are modal verbs:
Modal verbs are auxiliary verbs that express ideas like ability, necessity and prohibition.
Many modal verbs have more than one meaning.
They are always followed by the simple form of a verb (infinitive).
Example: Andrew has to pay his rent every month.
(This shows that Andrew has no choice. He has an obligation to pay his rent. He will be in trouble if he does not pay his rent.)
Let's read about how to express necessity or obligation. The modal verbs “must,” “have to” and “have got to” show that something is not optional; it is necessary.
Be careful! The subject and verb must agree for he/she/it subjects AND the question form requires “Do/Does/Did”.