Black metal is more an idealogy and belief than a style of music, though at its most basic level its more tremelo picked and high pitched than death metal. its "generally' more satanic and pagan and nihilistic, ive often compared black metal to 'winter' is if were to use a metaphor-cold, bleak and barren, though with todays genre mixing, there are black metal bands with non satanic idealogies and varipous levels of ambience, experimentation and other atmospheres (cyber, nature, folk, viking, etc) but so called 'real' black metal fans will be quick to call them false.
This might help
http://en.wikipedia.org/wiki/Black_metal
Black metal (and all its various offshoots) i'd recommenmd thats not silly:(in my opinion)
Wolves in the Throne Room
Lo-Ruhamah (A christian band)
Emperor (despite thier video)
Anaal Nathrakh
Leviathan
Bergraven
Deathspell Omega
Blood of the Black Owl
Ludicra
Cobalt
Dissection
Solefald
Watain
Melechesh
Secrets of the Moon
Sear Bliss
Negura Bunget