Non-copular uses

As an auxiliary verb:
To form the passive voice: "I was told that you wanted to see me"
To add continuous aspect to tenses: "It is raining"
Meaning "to exist": "I want only to be, and that is enough." "There's no sense in making a scientific inquiry about what species the Loch Ness Monster is, without first establishing that the Loch Ness Monster indeed is." "To be or not to be, that is the question." "I think therefore I am."
Note that the auxiliary verb function derives from the copular function; and, depending on one's point of view, one can still interpret the verb as a copula and the following verbal form as being adjectival. Abelard in his Dialectica made an argument against the idea that the copula can express existence based on a reductio ad absurdum (Kneale - Kneale 1962 and Moro 1997).