Red Hot Chili Peppers, SECC, Glasgow

The daddies of sock-rock sock it to the masses (and their hairdressers)

'You're the sexiest man on earth!!!" Anthony Kiedis probably can't hear the shriek of Scots approval from 50 yards distance, but I sure as hell can from one row away. But really? That big American mouth? The cartoonishly low brow? The wilfully ape-like demeanour? Then again, I was never going to understand this one. The Red Hot Chili Peppers could almost have been invented to get on my nerves. They represent an interpretation of masculinity which is at odds with everything I believe in, and I will, if pushed, admit that I'm always uncomfortable around men who are so at ease the world of the "physical", who will happily go onstage wearing nothing but socks on their cocks, and who can jump as high as their own shoulder without so much as a run-up. That said, something very strange has happened to Red Hot Chili Peppers lately. They open tonight's show with "By The Way", the lead-off single from their latest album, and "Scar Tissue", the lead-off single from the previous one. In both cases, you're struck by the overpowering seam of melancholia which runs through the otherwise-standard Chili-by-numbers music.

Of course, the new, mellower RHCP only makes them more widely marketable. The place is packed with a peculiar mixture of people who wouldn't have gone to a Chili Peppers gig 10 years back: kids who are strangers to the hairdresser, mums who are friends to the hairdresser, and... well, the hairdresser his- and herself.

But what are they actually so downbeat about? What's the matter with them? How bad can life be? You're living in God's own city, you're rich, thousands of young women want to have sex with you, and the sun never stops shining. There's a whole thesis to be written about the impossibility of truly moving, emotional music coming from a climate where it's sunny 365 days a year, but perhaps it explains why the lyrics to these songs are always half-thought abstractions. You never do find out what's getting Kiedis down.

Of course, more than half the time ("Suck My Kiss", "Don't Forget Me"), he's a crude priapic primate, a penis on legs. Even on "Scar Tissue", apparently a song about self-harm, he still finds time to do the nasty against a wall with a "young Kentucky girl in a push-up bra".

Despite the attempted upstaging by Flea, the world's least low-profile bassist (to me, he'll always be one of the nihilist kidnappers in The Big Lebowski), Kiedis is an undeniably impressive spectacle. At first, you think he's wearing one of those comedy "muscle suits", until you realise it's real. As he makes one of those pugnacious skips towards the mic, as though he's about to offer it out for a fight, you notice he has the glossy hair of a 10-year-old, not a fortysomething.

Today is guitarist John Frusciante's birthday, so he gets to have his minute in the spotlight, singing a solo cover version of some punk rock fossil or other. Just when you're thinking, "Yes, yes, very sweet, now move over," he stuns the whole room by belting out a 1950s doo-wop ballad, with much shrill repetition of the word "bay-bee", in an amazingly powerful girly falsetto.

Then he jams the riff from "Miss You", suggesting that he agrees with me about the Stones' best period being their sleazy, slutty, silk-shirted late Seventies. The one Chili Pepper I couldn't pick out of a police line-up totally steals the show. What are the chances of that? (A little research reveals that Frusciante has made a couple of solo albums, and I might just have to dig them out.)

There's something jarring about the juxtaposition of Scots puritanism and Californian excess. The Chili Peppers urge the kids to go crazy, to "Throw Away Your Television" and indulge in wild "Californication". The sign tells them that "Crowd Surfing Is Dangerous", and the sour-faced hag in the high-visibility jerkin bawls that "If you smoke another cigarette, you will be ejected" (actually at the bloke behind me, but for the second time, it's my eardrums that get a shredding). When four inflated condoms begin to float around the moshpit, I wonder where the hell such fun-oriented items were purchased.

Suddenly, a coil-sprung guitar loop thwacks you on the back. "Give It Away" is, of course, one filthily kick-ass slice of funk-rock. Back in 1993, it seemed just one of many flavours on offer. Little did we know that it was the sports-metal blueprint for the coming Reich of Limp Bizkit, Linkin Park, and a thousand lesser (imagine!) talents. The Chili Peppers were unwitting, and witless harbingers of doom, and if there was such a thing as a musical vasectomy, we should have given them one when we still had the chance. There have been times over the last decade that the RHCP asterisk, and all it has come to represent, has loomed as despised as a swastika in my imagination, and you can only hope that they gaze upon their offsprings' (and indeed The Offspring's) works in despair, sobbing "What have we done?!", like Robert Oppenheimer, only not as brainy.

The big question, of course, is: will they do "Under The Bridge", the song written about the overdose and death of their guitarist Hillel Slovak, now that it's been defiled by All Saints' lumpen version? (When the Appletons sang "I don't ever wanna feel like I did that day," you imagine they'd lost their Harvey Nicks charge card down the back of the sofa.) The answer, in the encores, is yes, but only when Flea has deflated any portentousness the song might have possessed by bathetically hand-walking across the stage.

All it ever takes to surmount even the most solid of ramparts is a cracking tune. It just so happens that Red Hot Chili Peppers' current single, "Can't Stop", is one. I hate to admit it, but it's quite brilliant: lean, taut, and possessing a kinetic inevitability. Finding myself praising a RHCP record is as unexpected as a slap in the face. Red Hot Chili Peppers will always be my adversary. But at least they're a worthy one.

s.price@independent.co.uk

Docklands Arena, London E14 (020 7538 1212), tonight; MEN Arena, Manchester (0161 930 8000), Tue & Wed