In Greek mythology, Apollo was the god of prophecy, the Sun, music and the arts.
Apollo's symbols were the lyre: an ancient, string instrument, the raven and the laurel wreath. Warding off evil, healing and protecting the young are associated with Apollo.
Apollo rides a chariot made from gold that was gifted to him on his third birthday. From his golden chariot he is known to deliver sudden death and sickness to mortal men as required. He has the power to heal as well as to destroy. Surprising, inexplicable death among males were supposedly caused by Apollo's arrows.
While Helios is the personification of the Sun, Apollo can be called god of the Sun. One cannot worship Helios, but one can worship Apollo.
The serpent had been sent by jealous Hera to plague Leto. Apollo matured instantly to adulthood after his first taste of ambrosia, food of the gods. He was then gifted with golden bow crafted by Hephaestus. With this bow and arrows he killed Python and established the sacred temple of Delphi on the site of his victory.
After killing the serpent there was a trial against Apollo, as he had killed one of Gaia's children. Despite Gaia's request, Zeus wouldn't send Apollo to Tartarus. Instead, he was to serve as a slave for nine years in the realm of mortal men. After receiving rituals of purification and rejoining Olympian gods, he had to protect his mother Leto once again from wrath of Hera, this time killing a giant named Tityos.
Apollo had many lovers (both men and women) throughout Greek myth, most notably Daphne, a nymph who transformed herself into a laurel tree; he later made the laurel his sacred plant in her honor, and Cassandra, a Trojan princess who he gave the gift of prophecy; when she rejected him, he cursed her, making her visions disturbing. Vision were to become true, but nobody was to believe her, leading to Troy's destruction.
When Apollo found the centaur Chiron who had been abandoned by his mother, he raised the centaur and taught him in every field of his personal knowledge. These teaching were complemented by Artemis.
Even though Apollo was generally a loyal son to Zeus, the two did have a serious conflict when Zeus killed Apollo's son Asclepius with a thunderbolt. Asclepius was a mortal man, who Apollo had taught so well in medicine and healing that he was able to bring people back from the dead. Hades complained to Zeus that Asclepius was stealing mortals from him. Zeus agreed that such power at the hands of mortals was not to be and struck Apollo's son dead with a thunderbolt crafted by the Cyclopes. As a revenge, Apollo killed most lesser cyclopes who had originally gifted Zeus with his signature weapon.