Ought to: Modal Auxiliary Verb

A modal verb is a type of auxiliary (helping) verb  that has no meaning on its own but it modifies the main verb, changes  its meaning and gives more details about the action. Ought to is a type of auxiliary modal verb used to express obligation and duty through advice or recommendations. https://open.books4languages.com/english-a2-grammar/chapter/ought-to-modal-auxiliary-verb/