Chaos A.D. was the record where everything came together for Sepultura, when they graduated from being an excellent, if derivative, band into one of metal's most unique voices. Their strident political dissidence is more focused than ever, referring explicitly to injustices in their native Brazil. The band's thick, chunky guitars, busy percussion, and hoarsely shouted vocals may be rooted in death metal, but it was often hard to call Sepultura a true death metal band, even if they flirted heavily with the style by way of Slayer; Chaos A.D. is rooted just as much in hardcore punk in its lean, stripped-down assault, featuring a cover of New Model Army's "The Hunt" and a collaboration with Jello Biafra on "Biotech Is Godzilla." At a time when '80s thrash giants like Metallica and Megadeth were streamlining their music for greater accessibility, Sepultura's aggression actually increased along with their tightened focus, borrowing from hardcore arguably more effectively than any other true metal band. Additionally, Sepultura began to draw upon the influences of their native Brazil, audible in the acoustic instrumental "Kaiowas" and in the way the band's complex rhythms move and breathe, to offer a much wider range than any of their contemporaries seemed willing to pursue. The band's songwriting became almost airtight, giving up the breakneck speed and long progressive passages borrowed from mid-'80s Metallica, and concentrating instead on creating texture and dissonance. But really, it's the unbelievably powerful rhythmic base provided by Igor Cavalera that gives Chaos A.D. its knockout punch. Endlessly playable (there isn't a wasted or unnecessary note on the album), passionately performed, and a sign that a new metal underground was finally bearing artistic fruit, Chaos A.D. ranks as one of the greatest heavy metal albums of all time. It's a remarkable achievement not only in its concentrated power and originality, but also in the degree to which Sepultura eclipsed their idols in offering a vision of heavy metal's future -- a vision that would only grow more compelling with their next release.