In 2008 your correspondent sat in a darkened hotel room in London, England with System of a Down's Daron Malakian and listened as the guitarist and songwriter explained in the frankest terms that it was his growing paranoia and resentment towards the star quality of lead singer Serj Tankian that had caused him to put one of the world's biggest rock bands on hiatus.

Three years later, System of a Down have reformed and returned. And for one of those rare nights, Vancouver was the centre of the rock and roll world as the second System show in five years (the first took place in Edmonton two nights earlier) engulfed Rogers Arena.

And yet, there was still an element of paranoia in the air. Media passes were impossible to come by. The swarms of photographers who'd normally be covering an event of this magnitude were notable by their absence. Perhaps the band wasn't quite convinced that they were firing on all cylinders yet?

Thirty seconds into the band's opening track, Prison Song, and it was like they'd never been away. Malakian, having shaved off the Taliban-style beard he was sporting back in London, looked lean and clean in a red dress shirt. Tankian, similarly smart in a crisp white button-up shirt, was vocally impeccable. The crowd, crammed onto Rogers Arena's hallowed floor, lost its collective mind.

If you've never heard System of a Down, it's not actually that simple a sound to describe. Hugely proud of their Armenian heritage, they've moulded the music of their forefathers into a modern heavy metal framework. Songs will lurch from chugging riffs to lilting ballads and back again, often within the space of a handful of bars. Traditional song structures are out the window. The effect, to the casual listener at least, is Fiddler on the Roof meets Iron Maiden.

It's not just the music that skewers rock conventions. Lyrics are awash with irony. "So you want to see the show / You really don't have to be a ho," crooned Tankian on Psycho. The song Cigaro, sang by Malakian with a devious smile, is even more brazen. Look up the lyrics for yourself.

The performance clung to arena rock protocol by the thinnest thread. The stage backdrops were simple printed curtains. Both stars launched into pirouetting folk dances with little prompting.

"Clap your hands simultaneously," instructed Malakian, before launching into another punishing blast of heaviness. "Any suggestions?"

Despite having three Multi-Platinum albums and one Grammy Award lining their trophy cabinets, System of a Down's commercial appeal remains elusive. Even their angriest, heaviest and catchiest riffs – on Chop Suey, BYOB and the set's finale, Sugar – are paired with noodling guitar passages or sections of old-fashioned baritone crooning. Somehow, just about, it works. By utterly rejecting the obvious, System of a Down are fascinating, even after five years away.

As for the rivalry between Malakian and Tankian, you'd have to be looking, but it's still there. For the duration of the two-hour monster set they barely exchanged glances, let alone words. During PLUCK, Tankian was on his knees reciting a monologue about the Armenian Genocide of 1915. Malakian responded to this touching tribute by dancing around the stage waving a sock above his head.

If all this weirdness creates the impression that this was anything other than a great rock and roll show, you'd be mistaken. Alternately ferocious and gentle, System of a Down left Rogers Arena with more questions than answers, but having inspired thousands of magical moshpit memories.

"Good luck to the Vancouver Canucks," smiled Malakian as the band finally strode off the stage.

Busting conventions doesn't mean there isn't room for good manners.