metal vocal styles are all over the place you get clean vocals mostly in your power and prog bands and sometimes goth and doom bands, guttural primarily used in black and death metal (lemmy kinda is the one who started it), thrash metal tends to be a lot of loud yelling (not screaming, screaming != metal). of course you have the high pitched so called "traditional" sound that was famous in the 80s. if you trace metal as far back to black sabbath you will find typical 60s rock style vocals. some bands even use classical or operatic styles. therion is a band that likes to mix classical arrangements with traditional metal to create an unidentifiable subgenre. arcturus did the same with more of an avantgarde twist. you of course have nightwish (though there are better fem vox bands out there, like theatre of tragedy). there are even chicks doing guttural (astarte, arch enemy).
point is metal is so broad that you may actually have to listen to a dozen different subgenres to find a style you like. i started listening to thrash before finding black and death, but these days i mostly listen to the old skool black metal (the stuff that came out before the generic norwegian sound was established), doom metal, motorhead (it gets its own genre), and whatever celtric frost/triptykon calls what its doing (t.g. warrior seems to be mixing up the things i like best about metal and sticking it in one band).
