I like most styles of metal, but doom metal is the major glaring exception. Doom metal spends way too long being slow (boring). I'm also incredibly picky with black metal; I find "traditional" black metal to be overly aggressive and annoying, but I quite enjoy many acts which employ black metal less dominantly (such as Sigh, Borknagar, and Ihsahn).
Favorite artists include Scar Symmetry, Blind Guardian, Sonata Arctica, Amorphis, Orphaned Land, Opeth, Vintersorg, and... I dare say... Avenged Sevenfold. They're criticized by all "true" metal fans everywhere, but they've delivered some top notch material. They're also responsible for getting me into metal around the age of 14.