The beauty of Disturbed is their lyrics imo. I think a lot of the songs' meanings have either to do with 1 of 3 things:
1) The war on terrorism.
2) Bad relationships.
3) Being a/the better person.
They've also got an incredibly catchy beat.
These are my favorite tracks, they really hit home with how I'm feeling:
The Sickness - The Game
The Sickness - Fear
The Sickness - Down With The Sickness
Believe - Liberate
Believe - Rise
Believe - Mistress
Ten Thousand Fists - Ten Thousand Fists
Ten Thousand Fists - Just Stop
Ten Thousand Fists - Guarded
Ten Thousand Fists - Deify
Ten Thousand Fists - Stricken
Ten Thousand Fists - Land of Confusion
Ten Thousand Fists - Sacred Lie
Ten Thousand Fists - Pain Redefined
Bonus Track? - Hell
Indestructible - Indestructible
Indestructible - Deceiver
Indestructible - Haunted
Indestructible - Criminal
And for the poster who claims Disturbed isn't really metal, from Wikipedia:
Heavy metal (often referred to simply as metal) is a genre of rock music that developed in the late 1960s and early 1970s, largely in England and the United States. With roots in blues-rock and psychedelic rock, the bands that created heavy metal developed a thick, massive sound, characterized by highly amplified distortion, extended guitar solos, emphatic beats, and overall loudness. Heavy metal lyrics and performance styles are generally associated with machismo and masculine sexuality.
I think Disturbed fits the above paragraph pretty well.