I think Apollo's relationship to the Sun is blurred a bit because he is often depicted in a similar manner as Helios; both young, handsome, boyish charm and good looks (The ideal of the kouros (a beardless, athletic youth)... both with auras of light crowning their heads.
But while Helios is associated the Sun only, Apollo is in fact one of the most complex deities in any pantheon. The son of Zeus and Leto, Apollo has been widely recognized as a god of light (and the sun), truth and prophecy, healing, plague, music, poetry, and more. Apollo also became associated with dominion over colonists, and as the patron defender of herds and flocks.
Without further ado... Apollo