Modal auxiliary verbs allow us to express notions of ability, obligation, repetition, etc. They also allow us to conjugate other verbs in tenses other than the present. Some commonly used auxiliary verbs:
• Can: ability to do something, possibility or permission:
Horatio can smell an animal in the jungle from miles away. Horatio is able to smell an animal in the jungle from miles away.
Susie can't come today. Susie is unable to come today.
Can I borrow this pen? Will you let me borrow this pen?
• Will: the future or wishes:
Bruno Delavigne will be here tomorrow. Bruno Delavigne is going to be here tomorrow.
I won't call him anymore. I don't plan to call him again in the future.
Will you stop making noise please? Please stop making noise!