Bristol tonight played host to the first night of a weeklong UK tour that will surely be remembered as one of the heaviest touring bills of the year anyone will put together.

First onto the dimly lit stage of an already busy O2 Academy, swigging from beer cans and vying for the position of most un-pretentious band in the world, is Portland, Oregon's Red Fang. I was unaware of the band, but within minutes they win me over with a simple heavy riffing style that falls somewhere between the groovier 'Sabbra Caddabra' style Black Sabbath and QOTSA, sprinkled with a little Hawkwind space dust. Half an hour is all they need to win many new friends, and they certainly make it onto my list for further investigation.

Next up, another new one for yours truly, is The Dillinger Escape Plan, launching an assault on our senses which to me sounded increasingly like an extreme metalcore version of Spinal Tap's legendary 'Jazz Odyssey'. Muscle bound frontman Greg Puciato seemed a little incongruous with the assembled masses' less than manic response to the band, obviously used to rooms full of people losing their minds rather than just a small hardcore, he questions politely "who doesn't know who we are?" Although with his imposing frame in mind I'm not sure he got an entirely truthful response from everyone.

They fair laid waste to every music rule in the book with their frantic interchanging of beats and riffs and red raw vocals, though at their more tuneful moments I couldn't help think they sounded little more threatening than say, LostProphets, but when in full flight you could not fault the intensity or execution they played with, and when Puciato hurled himself into the crowd for a second time you're left in no doubt as to what this band are all about; good, clean, violent fun.

Top of the shop tonight though is Atlanta, Georgia's current favourite metallurgists Mastodon. Out of the back lights with no bullshit and straight into 'Dry Bone Valley', and for the next hour and a half any memories anyone has of the previous bands is washed away, effortlessly raw, mercilessly blunt yet razor sharp all the while.

'Black Tongue' sees Troy Sanders centre stage, bathed in green light and looking like an apocalyptic warlock calling forth Armageddon, flanked by the superb dual guitar attack of Kelliher and Hinds. Last year's surprise hit album, 'The Hunter', features heavily in the set, and receives rapturous support for each track, yet old school fans aren't disappointed as favourites like 'Megalodon' and 'Bedazzled Fingernails' are unceremoniously battered into our heads.

Barely taking time for breath never mind sharing pleasantries between songs, this four piece crank out the most bone crunching yet tuneful heavy metal for an unforgiving ninety odd minutes, finishing up with support band Red Fang joining them for a rousing version of 'Creature Lives', and leaving the O2 Academy and its patrons in a state of metaphorical ruination.

This is a sound almost too big to contain in a venue so modest in size, and with momentum gathering behind Mastodon in light of the success of their latest album I wouldn't mind betting that these hoodlums take a step that's becoming more unusual all the time in metal, and that's the step into arenas. In fact, looking at the headliners of a certain metal festival this summer, you can't help but think something is really amiss that this lot are over looked in favour of yet another festival set from Metallica, some OAPs, and what I would only describe as a pop group. It's been a while, but surely it's time for a really heavy band to make that cross over again, and Mastodon, on tonight's showing, could one day rule the world.