Pop; Henry Rollins; The Forum, London

As the leader of the American metal-rockers Rollins Band, Henry Rollins exudes so much testosterone that you could grow a moustache simply by being in the same room as him. With his blank stare and sharp crew- cut, he might be Eagle-Eyed Action Man come to life. When he's not making a ruckus with records that go "Aaaarrrggghhh!", he occasionally undertakes spoken word performances, which also go "Aaaarrrggghhh!", only in a more eloquent and sophisticated manner. His last such show, Get in the Van, won him a Grammy. The latest, Public Insomniac No 1, bulldozed into London last Friday and proved that Rollins's obsession with himself has more to do with dogged self-deprecation than the narcissism suggested by those melon-sized pectorals and that suit of tattoos (both of which he kept covered, thank goodness).

For he had come to flex his mind, not his muscles. Within the first five minutes, Rollins was already perpetuating his violent image, waxing lyrical about the art of breaking noses: "The moment your fist connects," he babbled breathlessly, "it's like falling in love for the first time." An inventory of greatest hits followed ("Another time, I broke this guy's nose and the break was so righteous that the cop let me off.") This earnt some worryingly jubilant whoops of delight. But you felt that Rollins was playing games with the more susceptible elements of the audience, particularly when he went on to reveal how he uses his psychotic on-stage demeanour to disguise the nerd within, that bumbling nitwit who fluffs lyrics and is too short-sighted to find the microphone.

If there was a theme to the show, this was it: revealing the unseen. Rollins led us into the office of the throat doctor he shares with Michael Bolton, and around the sordid backstage area at the Grammys. Often, the probing was more literal, not to say visceral, as he enthused about touching his own skull through a head wound, and watching his tendons move after he tore his hand open. He remembered a kid from school, too, who had suffered intense burns and returned to class with his pigment eroded. "He had a strange depth and wisdom," Rollins mused, "because he had gone through pain and suffering to get where he was." There was an eerie calm to the image, perfectly evoking a child's fascination and revulsion, as well as an artist's masochism.

By the time a piercing attack on homophobia was underway, those susceptible elements were displaying the sort of restlessness that usually comes with a dose of crabs. Rollins positively bristled when it became clear that he was rubbing people up the wrong way; his enunciation grew crisp, his descriptions rhythmic and lucid, and he riffed gleefully on the tart image of a hardened homophobe using a taste-test to distinguish between hetero- and homosexual semen.

But there wasn't enough in the rambling three-hour show to keep Rollins riveted, let alone us. Each story juddered to a halt so abruptly that you expected the hiss of airbrakes, but the problem was content, not style. Too much of the material amounted to no more than showbiz tittle-tattle. And the punches Rollins threw were way off target; there were jokes here that Bobby Davro would have rejected. We need another dig at in-bred hicks about as much as we need to know how cheesy medallion men are, or what a hostile place New York is. Sadly, we heard all these things and more in a sort of Capital Gold of gag runs.

When he did get serious, in his aching recollection of visiting a fan dying of leukaemia, those airbrakes didn't kick in fast enough, and he concluded the tale with a desultory "My problems aren't so heavy after all." It may be a tough lesson for a man who makes a living out of ranting to learn, but some things really are better left unsaid.