Billy Bones is the hard-drinking, sea-chanty-singing pirate who first appears at the Admiral Benbow Inn seeking a quiet, out-of-the-way place to live. In many ways Billy Bones is a template for the rest of the pirates we meet in the novel (except for Long John Silver, who is utterly unique).
Like the other pirates, Billy is an alcoholic. He loves rum so much that, even after he has a stroke and Doctor Livesey warns him that he'll die if he keeps drinking, he can't stop. Billy Bones is also incredibly suspicious: he pays Jim Hawkins a small fee so Jim will keep an eye out for a one-legged man (we all know who that is). He keeps a locked sea chest, and when he finally meets one of his old comrades – Black Dog – they immediately set to sword fighting. Clearly, being a pirate is not a peaceful profession.
Billy Bones sets the scene for what kind of a novel this is going to be. Not only does he provide Jim with the treasure map that inspires the trip to Treasure Island (over Billy Bones's dead body), he is also the first character to sing, "Fifteen men on a dead man's chest, yo-ho-ho and a bottle of rum!" He tells fearsome, exciting stories that both terrify and excite Jim – tales much like Jim's own pirate tale, to follow.
Billy Bones proves the danger of a pirate's life, since he lives in fear of his own crewmates. But he also demonstrates the glamour and excitement of such a life, with his tall tales, strange way of speaking, and incredible charisma. Billy Bones serves as an introduction for the tale to come, and his sudden death provides Jim with the map he needs to set out on his own adventure.