This document discusses the main verbs and modal auxiliaries can and may in English. It defines main verbs as the important verb in a sentence that shows the action of the subject. Auxiliary verbs help the main verb. The modal auxiliaries in English are can, could, had better, may, might, must, ought, shall, should, will, and would. Can expresses ability, possibility, informal permission and requests, while may expresses polite requests with I or we, formal permission, and less than 50% certainty. Both are followed by the simple form of the main verb and do not take an -s ending with third person subjects.