Biohazard was founded in 1988 and was one of the first bands to mix heavy metal and hardcore with elements of hip-hop and rap; the resulting aggressive sound underlines vocalist/guitarist Billy Graziadei's tales of urban decay, crime, corruption, and social ruin. Formed in Brooklyn, the band's other members include guitarist Bobby Hambel, bassist Evan Seinfeld, and drummer Danny Schuler.
They formed Biohazard for the purpose of expressing political viewpoints and discussing problems facing urban youth, which all of the members had experience dealing with themselves. After the release of Urban Discipline, which attracted notice amongst punk and metal fans, the band followed the example set by Anthrax and Public Enemy's collaboration on "Bring the Noise" and performed on an alternate version of the hardcore rap group Onyx's hit single "Slam." The two groups also worked together on the Judgment Night soundtrack.
Their next album, State of the World Address, made the metal/hardcore and hip-hop connections even more explicit, featuring a guest appearance from Cypress Hill's Sen Dog.
Between their first and second major-label albums, Biohazard trimmed their lineup to a trio, which had the effect of focusing their attack. Where they have had the problem of being a little too diverse in the past, ricocheting from metalized hip-hop to rap-inflected hardcore, the band has now concentrated their energies into creating a singular, piercing sound. There are still elements of metal, rap, and hardcore punk on Mata Leao, but they are fused into a cohesive whole, which makes the album more effective than the previous record.
Biohazard still has a problem with writing strong riffs and convincing lyrics, but music has more power and finesse than their previous releases, and that actually sounds better than the raw, edgy chords that powered their intial indie records. After the recording of Mata Leao, Rob Echeverria became the new guitar player of the band.