In 1990, Pantera released their fifth album, Cowboys from Hell, which ushered in a new wave of hard-driven hard rock, later labeled as "groove metal." While bands like Exhorder had already dabbled in similar sounds, it was Pantera—whether for better or worse—who became the poster band of this movement, influencing countless mishmash genres all the way to 2024. Having experimented with grooves to a minor extent on their previous album, Power Metal, Pantera fully embraced this direction on Cowboys from Hell, incorporating riffs that differ from their glam-leaning past and could be described as hard rock or Southern rock. At the same time, they borrowed break riffs from thrash metal and repurposed them as main riffs, adding what they might consider an "experimental" touch. The result is an album filled with heavy, pounding thrash breaks and distorted, groove-laden hard rock riffs. In any case, this album marked Pantera’s commercial breakthrough and set them on the path of becoming the pioneers for a generation of "metal posers."

The tracks on the album can generally be divided into two categories: those focused on hard rock riffs, and those centered on "pretending to be thrash." The former is represented by the title track "Cowboys from Hell," one of their most famous songs, while the latter is exemplified by tracks like "Heresy." "Cowboys from Hell" is often cited as a quintessential groove "metal" track, yet it offers very little that could be considered a genuine "metal" riff as previously defined. It’s a song built around hard rock riffs with heavy distortion and a bouncy groove, structurally uninspired and unremarkable, though not entirely unlistenable. The other well-known track, "Cemetery Gates," blends a Southern rock atmosphere with simple power chord-based metal riffs, resulting in a listenable yet still mediocre song. "Shattered" could have easily fit on Power Metal without feeling out of place—it's a hard rock-influenced heavy metal track, also decent but nothing extraordinary. "Clash with Reality" similarly falls into the category of hard rock riff-driven songs.

However, the real problem with this album—and with the groove metal genre as a whole—becomes clear in the second category of songs. These tracks all share the same trait: they take riffs typically used as break riffs in thrash metal, especially those with a prominent groove, and turn them into the central theme of the song. Traditionally, thrash break riffs serve as a contrast to faster riffs, providing tension and a breather. But when these riffs become the entirety of a song, it leads to monotony and frustration, reducing the music to nothing but rhythm. Pantera didn’t stop at simply adopting thrash breaks. They created groove breaks—the kind of riffs that later bands in groove metal, metalcore, and deathcore would adopt, stripping everything away except the rhythm, practically forcing the listener to engage in mosh pits or slam dancing. It may be considered their "achievement," but for more traditional metal fans, riffs like those found in the coda of "Domination" or the main riff of "The Sleep" can only be described as a nightmare.