Before Limp Bizkit and Kid Rock came Biohazard. Taking their lead from the thrash-hop hybrid pioneered by Anthrax's classic collaboration with Public Enemy on "Bring the Noise," Brooklyn's Biohazard spent the early 1990s mining the previously under-exploited overlap between hardcore metal and hip-hop cultures. In retrospect, the combination was a natural one: both types of music were vehicles for the expression of rage and disaffection. Biohazard made the fusion seamless with Urban Discipline. Vocalists Billy Graziadei and Evan Seinfeld swap lyrics over a backdrop of heavy beats and heavier guitars. Biohazard had a genuine political agenda: songs like "Punishment," "Loss," "Mistaken Identity," "Hold My Own," and the title track are rallying cries against the pitfalls of the urban scene that spawned them. Biohazard continued to make great albums, but Urban Discipline stands as the album that influenced an entire scene. For aficionados of hip-hop and heavy metal, it remains an essential purchase. --Robert Burrow