Patron of the arts, of music, and epitome of manly beauty.
Being considered perfection in all things, Apollo has, perhaps understandably, developed an ego the size of Mount Olympus. Like Narcissus, there is little he would like more than to spend eternity gazing at his own reflection.
Apollo's twin sister Artemis considers him a damn nuisance because of the gaggle of squealing nymphs which inevitably attaches itself to him when he walks in the forest. He in turn considers she's being ridiculously uptight by insisting on remaining a virgin.
His relations with his half-brother Hermes are similar. Apollo considers Hermes a childish nuisance and Hermes thinks Apollo is a prat.
Apollo's attitude to mortals mirrors that of most gods. Mortals are there to provide services - prayers, sacrifices, sex, care of livestock - and that is all. There's no need to treat them with real respect or consideration. Apollo's shepherds, Nikos and Alexandros, are acutely aware of this.
As for why he wanders about in the nude... Have you ever seen a statue of Apollo wearing clothes?