Modal verbs, which express a likelihood, ability, permission, request, order etc., usually help main verbs to state the future. It is the reason they are categorised as auxiliary verbs in the context. While other auxiliary verbs such as is, are, was and were help relevant verbs to form the continuous tense, the modal are normally associated with the future tense. Examples are will, shall, may, might, can and could:
I can go tomorrow.
I will go tomorrow.
I may go.
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