Death metal, and in fact, most of modern metal originated from underground bands during the hair metal days, and most of the bigger ones hail from Sweden, particularly Gothenburg. The exceptions to this are nu-metal
, which is based in more than one way off of grunge
, and classic/stoner rock. The music generally consists of screams and yells, more high-pitched than not. They also have utter walls of guitar, accompanied by difficult-to-play leads, and drumwork second only to jazz. Also tends to have a recurring bass line; and guitars are oftened tuned down two steps or more. They sometimes tend to have a softer side as well, with orchestras or pianists. Lyrics, however hard to hear, are normally about important issues relating to the state of things, personal conflict, or political anthems. Major names from this genre: Arch Enemy, Opeth (much more of a softer side than most, one of the best bands there is), Soilwork, In Flames, Dark Tranquil(l)ity, etc. On another note, people who listen to nothing but metal tend to be fiercely defensive of their favorite bands, and do not like change, as any In Flames fan will tell you. They tend to have a love/hate relationship with any band they listen to. I personally don't think there is such thing as a bad song, just a less good one.
Death Metal: Arch Enemy, Opeth, Soilwork, In Flames, Dark Tranquil(li)ty, Darkest Hour, At the Gates, etc.
Not Death Metal: Emperor, Cradle Of Filth, Dimmu Borgir, Hypocrisy, Avenged Sevenfold, Stratovarius, Rhapsody, Korn, Linkin Park, Breaking Benjamin, Mudvayne, etc.
Slipknot has there own genre, because by most standards, they're a little bit of everything...World Music?