All modal verbs are auxiliary verbs, which means they can only be used with a main verb. Modal verbs cannot be a main verb. They are used to express ideas such as possibility, prediction, speculation, deduction and necessity.
On Twitter, I recently shared an excellent article by Justin Tarte called 5 Questions Who is doing a majority of the talking in your classroom? "It’s the person who is doing most of the talking that tends to do most of the learning." Great questions to ask ourselves as we are teaching!