Hah! How long is a piece of string?
You've got your basics: Trad, Thrash, Doom, Death, Black, Prog, and Power. The Seven Deadly Sins.
Then you've got a potentially infinite number of other styles and sub-styles that you'll almost certainly misunderstand and use in the wrong way, annoying both the elitists, who'll think you're a poseur and call you gay, and the non-elitists who'll hate you for being an elitist and call you "tr00".