CALGARY - Sometimes, to open a mind, you must use force. A hammer. A sack of doorknobs. Or, in the case of Armenian-American rock act System of a Down, a rhythm section plucked straight from a construction site and a guitar you could carve a side of beef with.

All the better to cram into your cranium the band's socially and politically charged material. And, as was the case last night at the Saddledome in front of a crowd of 12,000 or so, all the better to put on one of the best, one of the most intelligent and one of the most memorable arena metal shows to come through this city in ages.

It was the antithesis -- some might say the antidote -- to this year's double dose of Crue concerts.

System, like, say, Tool a couple of years ago, showed metal can be heavy, loud and brutal enough to knock you senseless, while knocking sense into you at the same time.

They showed you don't need contortionists and midgets when the music and message are powerful enough in their own right. In fact, the bare stage, simple lighting and lack of excess energy exuded in on-stage antics was barely missed when you were bludgeoned with the throbbing, relentless sonic attack of the quartet's superb musicianship.

Leading off with Soldier Side from behind a spotlit curtain and B.Y.O.B from their latest album Mezmerize, SOAD offered a healthy barrage of material from that album, their self-titled debut, even their rarities album and most importantly, their career-making, groundbreaking release, Toxicity.

Again, frontman Serj Tankian seemed, at times, to be going through the metal motions, but his whisper-to-a-primal-scream more than made up for it.

As did the rest of the band, who induced the crowd into a sea of clap-happy moshers with their good-natured goading and semi-spastic soloing, including a brief blood-letting from guitarist Daron Malakian, prior to a blistering, yet oddly moving version of Mezmerize's answer to the Bush administration's answer to Sept. 11, Sad Statue. And then, later, a reworking of Dire Straits' Sultans of Swing into a more personalized version.

It just kept coming -- the ferocity, the force and the filling for that forcefully pried-open mind.

And they didn't insult their audience by coming on for a predetermined encore -- they played long, they played loud and they played smart.

Setting the challenging note for the rest of the show -- although maybe setting the experimental bar a little too high -- were Sacramento noise merchants Hella.

Watching their baffling, filling-rattling set, you couldn't help but feel violated. The feedback-heavy structurally retarded sound orgy was akin to being dropped inside an Escher print and beaten through the confusion by a board with a nail in it.

Is that a good thing or a bad thing? I'm still not sure. Next up was the psychedelic space odyssey of The Mars Volta.

Years ago, in the very same Saddledome, Sonic Youth opened for Neil Young in one of the most polarizing warm-up performances I've ever seen. Knowing Young's classic rock fans, it was easy to understand the animosity and downright aggression directed at the NYC alt-rock pioneers.

But last night, the venom directed by a little less than half the audience towards the odd, but nonetheless accessible Floydian and Hawkwindian soundscapes created by the brilliantly out-there outfit was rather disappointing, especially considering the cannabis cumulus hovering inside the 'Dome.

Musically and visually -- the light show and backdrop were fittingly trippy and afroed frontman Cedric Bixler Zavala was an awe-inspiring and entertaining cross between James Brown, Prince and Beck -- The Mars Volta's brilliant hour-long experience was as high as you can get while still being tethered to this Earth.