Answer the questions

What has been the commercial juggernaut of alternative metal?

At its outset, alternative metal was a style united by its nonconformist sensibility rather than any immediately classifiable sound. Heavy metal was at the core of the music, but the bands were too offbeat and their influences too eclectic to fit into the thrash underground, so their main audiences were mostly alternative fans who liked heavy guitar rock. However, after grunge helped make alternative metal more palatable to mass audiences, it became the most popular style of heavy metal in the '90s, particularly when more aggressive bands began standardizing its sound.

That approach was a far cry from alternative metal's early days in the late '80s, when it represented the least categorizable heavy music around. By that time, most surviving hardcore punk bands had moved into metal territory, pushing underground hard-guitar-rock bands to look elsewhere for inspiration. The first wave of alternative metal bands fused heavy metal with prog-rock (Jane's Addiction, Primus), garage punk (Soundgarden, Corrosion of Conformity), noise-rock (the Jesus Lizard, Helmet), funk (Faith No More, Living Colour), rap (Faith No More, Biohazard), industrial (Ministry, Nine Inch Nails), psychedelia (Soundgarden, Monster Magnet), and even world music (later Sepultura). There was no real "scene," just an increased willingness to experiment with a form that had grown overly reliant on pure instrumental technique. Some of those bands eventually broke out to wider audiences, often with help from the Lollapalooza tour, and they also set the stage for a new wave of alt-metal that emerged around 1993-94, centered around the rap-metal fusions of Rage Against the Machine and Korn, the grindingly dissonant Tool, the heavily production-reliant White Zombie, and the popular breakthrough of Nine Inch Nails.

These bands would become the most influential forces in shaping the sound and style of alternative metal for the rest of the '90s, along with Pantera, whose thick, molten riffs sounded like no other thrash-metal band. Like many alt-metal bands, Pantera was serious, bleak, and inward-looking, but they demonstrated how to be macho about it. By the latter half of the '90s, most new alt-metal bands were playing some combination of simplified thrash, rap, industrial, hardcore punk, and grunge. This new sound was more about grinding textures and intense aggression than hooks or memorable riffs, and accordingly relied more on studio production to achieve its force; however, it captured the adolescent machismo that has long been mainstream metal's stock in trade, and accordingly became a commercial juggernaut. Korn, Marilyn Manson, and Limp Bizkit were the biggest stars of this new movement -- sometimes dubbed aggro-metal, nu-metal, or (incorrectly) hardcore -- and by the end of the decade, countless new bands were performing that style in a major-label feeding frenzy similar to the proliferation of hair metal bands in the late '80s (ironic, given alternative metal's vehement rejection of hair metal's attitude).