Rodrigo y Gabriela, Hammersmith Apollo, London

It's not hard to pin labels on the guitar-slingers from Mexico City, Rodrigo y Gabriela. They play metal with acoustic instruments; are described as "world musicians" (more because of their country of origin than their actual music, which mines the metal legacy to its core); and represent a kind of post-rock, post-irony phenomenon of our times whereby a full house can roar in near-hysterical approval at the couple's layer-by-layer undressing of the old Led Zep warhorse "Stairway to Heaven" without the slightest shame.

An American reviewer called them Metal Mariachi, but first and foremost they are guitarists, pushing their plugged-in acoustic models as far as they were designed to go, and then a bit further. Believe the hype: the ferocity, intensity and control of their technique is extraordinary.

Tonight kicked off a mini-tour taking in Glasgow and Manchester, and their first gigs here since the summer- festival season. The two appear beneath a giant screen, and with two either side, for the live, rapid black-and-white VJ-ing of their performance that adds a vital visual layer to the music.

After some metal fist-waving to the crowd, Rodrigo begins to pick and hit the body of his instrument at once, a kind of hard-cop, soft-cop guitar interrogation that fuels the delicate-to-driven template of songs such as "Tamacun" and Metallica's "Orion", staples of their setlist and highlights of their debut album.

As for Gabriela, she takes the guitar pummelling to even greater levels of intensity, summoning up a full-kit drum battle on the body of her guitar with extraordinary facility. There seems to be a whole rhythm section hiding in there, and stadium acoustics to boot. Even more impressive is the fact that the guitar doesn't swing wildly out of tune.

For much of the set, they're perched on their low chairs, bent over their instruments, headbanging as the riffs rise and fall, cut with fluid runs and flourishes from Rodrigo. Apart from being staggeringly good musicians who must have metal fingers as well as strings, they are superb workers of an audience.

"Tell us what to play and we'll play it!" shouts Rodrigo, and from there they hit the floor running, encouraging the kind of audience participation you don't see outside of panto, with the balcony doing one clapping rhythm, downstairs doing another, and the duo riffing ecstatically over the top.

The result, as Rodrigo would say, was awesome.

Rodrigo y Gabriela play the Manchester Academy tonight