Metal has as many subgenres as it has detractors. There's thrash metal, speed metal, power metal, black metal, symphonic metal, viking metal, prog metal, folk metal, stoner metal, and unfortunately nu-metal (slipknot falls into this category, and rightly so, as pretty much all nu-metal bands are worthless) … there's even jazz metal! Seriously, check out Cynic, Atheist, and watchtower if you want some jazziness thrown into the mix.
Slayer is one of the four (or five or six, depending on who you ask) godfathers of THRASH (with Metallica, Megadeth, Anthrax… and Exodus and Overkill). Those band pictures that you can google and get a good laugh from? Those are black metal bands.
If you want a good death metal album, get The Sound of Perseverance by Death. If you want more good thrash albums, turn to the early material from those 6 bands I mentioned above. Thrash is also seeing a re-emergence these days with bands such as Municipal Waste and Evile.
http://happydays.blogs.nytimes.com/2009/10/06/dance-with-the-devil/?apage=6#comments
More bands:
Black Sabbath
Burnt by the Sun
Dimmu Borgir
Hatebreed
Apocalyptica
Pantera
Lamb of God
Morbid Angel
Iron Maiden, "Number of the Beast"
Anthrax
Cannibal Corpse
White Zombie
Danzig
Bathory
Wolves in the Throneroom
Gorgoroth
Kreator
Emperor
Helmet
Sepultura
Cathedral
Bad Brains, "Quickness"
Pentagram, "Day of Reckoning"
Burzum
Mudvayne
Meshuggah
In Flames
what people fail to get about slayer is that virtually the entire project is about holding a mirror up to society. the band projects a deeply ironic point of view underpinned by humanistic values; it is an expression of total outrage. their early work reveled in satanic imagery as a way of taunting the christian world with its own invention. as the band grew, they didn't need to look any further than the society around them for creative inspiration. virtually everything they write about forcefully narrates an aspect of the human condition or historical situation that too many people choose to remain willfully ignorant of–while unconsciously creating it.
Legitimate metal is some of the most intricate, precise and brilliant music on earth.
http://happydays.blogs.nytimes.com/2009/10/08/life-after-death-metal/