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.
:: Tenses: Past + Present + Future x Simple + Continuous + Perfect + Perfect Continuous https://www.facebook.com/EnglishIF:: And to think I shrink from tutoring English because I don't know this stuff (and can't ever keep which and that straight). Evidently (obviously) it can be learned. Shame on me!