Modal Usage Example can ability, permission She can swim. / Can I go out? could past ability, polite request He could sing well. / Could you help me? may possibility, permission It may rain. / May I come in? might lesser possibility We might be late. must strong obligation, certainty You must do your homework. shall future (formal), offer Shall we begin? / I shall return. should advice, expectation You should eat healthy food. will future, willingness I will call you tomorrow. would polite request, imaginary situation Would you like tea? / I would travel if I had money. ought to moral duty You ought to respect elders. need to necessity You need to study harder. used to past habit He used to play football.