Phaethon thinks that his father is Apollo the sun god because his mother had told him but none of his friends believed him. So when he found the sun god he asked him whether his mother was lying to him or not. Apollo confirmed his belief that he was in fact his father but then realized his friends would still not believe him so he asked his father for a token or something so that they would believe. When he said this Apollo said he could have anything he wanted so he chose to drive the sun chariot for a day. Apollo as much as he wanted to say no had to let him because he had sworn to the River Styx and that kind of promise could not be gone back on so he had to let him. Once Phaethon had left it was not long before the horses thought they had no driver because he did not have the strength of a god and it was not long before he crashed almost setting the earth on fire but Zeus struck him and his horses into the ocean with a thunderbolt.