Fury Links System of a Down, Slipknot

Rage comes in many flavors. For Slipknot it’s all about cartoon horror, a dark but ultimately safe metal nightmare fantasy. System of a Down digs deeper, matching the same speed and aggression, while exploring complex textures that suggest the musical and thematic scope of a modern Led Zeppelin.

Both of these versions of contemporary metal were unfurled at Saturday’s Pledge of Allegiance tour stop at the Forum, which also included sets by Rammstein, Mudvayne and No One. But co-headliners Slipknot and System of a Down would have been better served leading concerts of their own, where fans might have seen more fully realized sets.

Though limited to barely an hour on stage, System at least played with fury and real finesse. The Forum show was also a homecoming for the Hollywood-based quartet, and System’s first local appearance since its sophisticated new album, “Toxicity,” debuted at the very top of the album chart this month.

The immediate impact of “Toxicity” was underlined as many fans sang along with most of the band’s new material, beginning with the urgent whispering that opens “Prison.”

Not that singer Serj Tankian needed assistance. Like Deftones vocalist Chino Moreno, Tankian is among the most versatile and distinctive young voices in hard rock, as convincing with an unsettling roar as in moments of quieter vulnerability.

If System is often seen as a brooding, politically aware unit, there was also dark comedy in the sex romp of “Bounce.” And the band was able to re-create the layered sound of “Chop Suey” and other songs without being limited by them, adding surprising new musical interludes.

Unlike System, the music of Slipknot is evocative of little more than anger and noise, which has its place on the metal landscape, but it’s also easy to come by.

High energy and a dizzying, fully realized horror fantasy persona are what make the band different, and helped keep the crowd excited even as some System fans left before Slipknot’s closing set.

In their macabre masks, matching jumpsuits and waves of fog and explosions, the band offered as many visual rewards as KISS ever did, down to the pair of “666” signs flanking the band.

Percussionist-vocalist Chris Fehn also jumped down from the stage to sing into the faces of ecstatic headbangers up front. There was no pulling back on the violent imagery, nor was there any connection to reality.

The band offers little in the way of variety, but Slipknot did add a modern, frenetic twist of electronic and turntable sounds to the likes of “Disasterpiece.” There was also the occasional snarky riff pattern, though it usually failed to fully pay off.

The sound mix at the Forum was wildly inconsistent, the quality depending mostly on where fans happened to be seated.

But support act Rammstein managed to cut through the muddle with music that mixed metal fury with dynamic guitar and keyboard melodies not unlike Powerman 5000.

And there were so many explosions in Rammstein’s set that the special effects man should be credited as a full band member.