I used to consider myself a metalhead, but when a band I like has 4 different albums that are 4 different kinds of metal, 3 of which I really like but 1 that I don't, it's hard to say "I like this band" because you have to be really specific, "I like this band, but only these albums". Especially when they vary their sound WITHIN the album, "I like this band, but only these albums, and only these songs of these albums". It's irritating to have to explain.
Not to mention you have to sometimes change your opinion of a band as time goes on. For example, Cradle of Filth creates a different sound with every new album they make. Midian is one of my favourite albums of all music and I really like Nymphetamine, but a lot of their other albums bored me after a few listens and others I just can't stand at all. Other bands like Arch Enemy and Nightwish change drastically by changing their singer. Arch Enemy went from "good guitars, but don't really care for the total package" to "wow, I fucking love Arch Enemy!" with the addition of Angela Gossow, while Nightwish went from "THIS SHIT IS SO FUCKING GOOD" to "Man... I miss Tarja
" with the addition of Anette.
These days, I consider myself someone that enjoys good music and I just know that I like a lot more metal than I do of any other kind of genre of music. I'm also much more critical of metal than any other genre of music /shrug