PHILADELPHIA -- A sub-freezing Philly was the setting for the Relapse Contamination Festival, a two-day event showcasing the best in metal, heavy rock and grindcore, all from the staple label in that scene, Relapse Records.

Saturday's kickoff at the legendary Trocadero club consisted of Bongzilla, Alabama Thunderpussy, Cephalic Carnage, Mastodon and Neurosis, who were playing their first East Coast gig in three years. The Trocadero was packed early for the show and the fans seemed like an army, uniformed in work pants, jeans, black sneakers or boots, black hooded sweatshirts, ski caps and big work coats -- even the girls.

First up was Bongzilla. The band takes thick, Black Sabbath riffs and combines them with screeching vocals and weird mood shifts. During their opening song, guitarist/vocalist Mike Makela blew out his amp, and there was a bit too much downtime before the group resumed its set and continued to play songs from its new album, Gateway, as well as older material. All in all, Bongzilla were capable but a bit boring. Their songs are great but their stage presence is a little less than exciting.

The next band out of the stable was Alabama Thunderpussy, who hit the stage with all cylinders firing. They're straight-up killer, smash face, southern rock, like ZZ Top with a trash metal infusion. Frontman Johnny Throckmorton was in full Ronnie Van Zant mode, swinging the mic stand and ripping through songs off their new album, Staring Into the Divine. Guitarist Erik Larson (ex-Avail drummer) said after the show that he's putting out a solo record called Resounding on Small Stone Records. "I played everything except bass," Larson said. "It's different than anything else I've done."

After the moonshine metal of Alabama Thunderpussy, it was time for the straight death metal sounds of Cephalic Carnage. Cephalic is your basic prog-metal, face-bashing, ear- bleeding music. The band seemed to be able to bring to life some of the songs off their album Lucid Interval which lay flat on the record itself. However, as good as Cephalic were, nothing could prepare the audience for the power and tight-as-hell live show of the new band on the scene, Mastadon.

The crowd had been buzzing about Mastodon all night, especially about the tension between them and grindcore kings Today Is the Day, who were playing Sunday. It seemed that Mastodon drummer Brann Dailor and guitarist Bill Kelliher -- both former members of Today Is the Day -- left the band on less than good terms. Fans felt tension between the groups, but a Relapse representative said, "That's simply not true. They're civil to each other." Mastodon took to the stage and crushed through their 40-minute set of songs from their 2002 debut, Remissions. Mastodon could be considered the second coming of Metallica and Rush combined, and nobody who's seen them live could counter that opinion.

The long-awaited apex of day one came when Neurosis hit the stage. They brought the crowd to its feet, where it would stay for the rest of the show. Neurosis' slow, sludgy sound grew slowly until it enveloped the audience. Complete with constant moving images behind them, Neurosis are not just a band to see, they're an experience that makes you sit, thinking dark thoughts about your life and those you love. Using space, heavy riffs, slow pacing and time changes, Neurosis became a single-minded living machine that moved the audience, dissected us, and then put us back together. Blowing through songs stretching from Enemy of the Sun all the way to their new album, A Sun That Never Sets, Neurosis delivered the show fans wanted to see after three years: big, scary, sensitive and totally honest.

The next day, Philly was still freezing but the crowd returned to the Trocadero to witness the advance screening of Neurosis' new DVD for A Sun That Never Sets. The DVD had lots of eclectic art pieces, snippets of videos and other visual themes over music from the new album, but it was an odd way to start a rock show. The crowd seemed a bit listless, but that ended as soon as Pig Destroyer hit the scene, slapping the crowd awake with their skull-crushing, no-nonsense grindcore. They mostly played songs off their new release, Prowler in the Yard, and one untitled track off their upcoming unreleased LP. The crowd went nuts, kicking up more pit action than the night before.

Almost as soon as Pig Destroyer were off the stage, post-hardcore grind masters Burnt by the Sun were out and unleashing on the crowd, with Dave Witte proving why he's one of the greatest drummers out today. Burnt by the Sun did almost the entire new album and seemed to hold the energy that Pig Destroyer had created. The band rarely disappoints.

Next up was the most insane display of the evening, from Today Is the Day. Though not everybody was happy with their new two-disc release, Sadness Will Prevail, Today Is the Day brought it to the crowd in a big way. By the end of their set, frontman Steve Austin had thrown his $2,500 Paul Reed Smith into the crowd and bassist Chris Debari had a head gash, complete with blood. Not everybody loved it, but nobody took their eyes off of it.

The final two bands of the night were High on Fire and the Dillinger Escape Plan. High on Fire proved they are rock gods by playing a fierce combination of Celtic Frost heaviness and the rock sensibilities of Kyuss or Black Sabbath. They stomped through songs off last year's Surrounded by Thieves and threw in a cover of Venom's "Witching Hour." Ending the whole festival was the Dillinger Escape plan, the grindcore/metal outfit that sounds like calculus played through loud amps and tuned down to heavy-as-hell tuning. Sometimes violent, often hard to listen to but always cutting edge, Dillinger had the most interesting set of the night with two covers (Nine Inch Nails' "Wish" and Aphex Twin's "Come to Daddy") as well as a small fire breaking out onstage thanks to a pyro mishap. I was hoping against hope that Mike Patton would show up onstage since they'd worked with him on the new Dillinger EP, Irony Is a Dead Scene, but no such luck.

When relative quiet returned to the Troc, a drained but satisfied crowd funneled out into the single-digit temperatures. Pondering the possibility of making this an annual event, one of Relapse's bigwigs, Carl Schultz, said, "I don't know, but it'll be next year, definitely."

For more sights and stories from concerts around the country, check out MTV News Tour Reports.

-- Iann Robinson