He is the son of Zeus and Leto, the twin brother of Artemis, and leader (and sometimes lover) of the Muses, functioning as their chorus leader and choreographer (Musagetes; "leader of Muses"). He invented the lyre, and mastered it. This just seals his rep as the archetype for all pretty-boy guitar-wielding frontmen everywhere. And like those frontdudes, he could be a real jerk sometimes. The consequences for losing a music contest against him were a tad harsh. Marsyas, for example, was flayed alive by Apollo.
Despite his star status, he was not above playing weddings, such as the marriage of Eros and Psyche, and Peleus and Thetis. He liked to party, hanging at the Bacchanalia with the maenads and satyrs.