They may not be household names for many U.S. metal fans, but the Mexican superstar duo Rodrigo y Gabriela has never been shy about paying tribute to its heavy roots -- and they recently received some superstar assistance in the form of Metallica bassist Robert Trujillo.

Trujillo, who has popped up at a number of Rodrigo y Gabriela gigs over the years, was on hand during their Aug. 17 show at the famous Red Rocks Amphitheater in Colorado, and took the stage to add some extra bottom end to a medley of Metallica covers. You can see a portion of the show courtesy of the fan-shot footage above.

Gabriela Quintero explained their affinity for metal in a 2002 interview with Cluas, saying, "Like a lot of Mexican youth, we were heavily influence by American metal bands -- Metallica, Megadeth, Pantera and also Sepultura. It was a full band, very loud, and for vocals, Rodrigo would just scream. We played this way for seven years."

Over the years, Rodrigo y Gabriela have expanded their sound, notching worldwide hits along the way, but they've always maintained a connection to those aggressive early years; their 2004 live album includes a cover of Metallica's 'One' (containing elements of the Dave Brubeck classic 'Take Five'), and they covered 'Orion' on 2008's 'Live in Japan.' Their most recent effort, '9 Dead Alive,' was released in April.