Simon Price on Rihanna at Cardiff's Millennium Stadium: Don't mess with the girls from the Valleys

Anew adjective is needed to describe a Rihanna concert: "pertory" (perfunctory minus the funk). In nearly 30 years of writing about music, I don't think I've ever witnessed a major star look so bored. I've seen mannequins at H&M more engaged with what they're doing.

For much of the Diamonds show, the singer can't even be bothered to disguise her contempt for the audience. She doesn't even pretend she isn't miming: at one point she holds the microphone closer to the crotch of her brocade hotpants than her mouth while the vocals, studio-perfect, continue uninterrupted.

Backed by six equally listless dancers, with Nuno Bettancourt from Extreme doing the occasional widdly guitar solo, she's desperately lacking in dynamism. A reluctant leg in the air, an I'm-a-table pose on all fours, a flick of her Charlie's Angels hair and that's your lot. Like an apprentice at a sewage farm, she's going through the motions.

"Cardiff! I hear you like to get rrratchet!" she says, probably after checking the back of her hand to see which city this is. "Ratchet" is a mostly uncomplimentary slang term (look it up on Urban Dictionary), and the wrong DIY tool for this crowd in any case. Ratchet? Maybe. Hammered? Definitely.

All day long, Valley Lines trains have been disgorging hard-partying proxies for the stars of MTV's The Valleys and BBC3's The Call Centre on the platforms of Cardiff Central, dolled up to the elevens and leaving drained pitchers of puce-coloured alcopops in their wake. They're magnificent, and do more to push the closed-roof cauldron of the Millennium Stadium towards boiling point than robo-Rihanna ever could. They are, literally, twice the woman she is. They don't need her.

What's pulled 65,000 of them here? Not magic, but mathematics. Rihanna has no mystique on her side, no star quality to speak of. Merely that lesser commodity, celebrity: the tawdry accumulation of Youtube hits and magazine covers. And it's the 65,000, more than she, who create the best moments, drowning her out through a thick, bass-heavy "Umbrella".

"Cardiff what the ....?" the Barbadian asks rhetorically. After the show, many of this Welsh assembly will wake from their slumber thinking "WTF?" too. Within minutes of the encores, their false consciousness is already starting to evaporate. Back on the platform for Radyr, I overhear one straight-talking Valley girl deliver her verdict. "Orr, she's shockenn! She got a nice arse, but that's about ett."

Say what you will about Kings of Leon (02, London ***), there's always the danger something will go entertainingly wrong. Even if you're not a fan of their Southern rock shtick – good ol' Tennessee boys, sons (and nephew) of a preacher man, playing the Devil's music – you have to grant them that.

At the Reading Festival in 2009, singer Caleb Followill reacted to perceived audience apathy with a rant that ended with a middle-finger salute and a smashed guitar. The following year in St Louis Amphitheatre, they cut a show short after pigeons in the rafters defecated in bassist Jared Followill's mouth. And in Dallas in 2011, a drunk Caleb went offstage to vomit and have another beer, but never returned. The rest of the tour was cancelled, with Jared tweeting "I can't lie, there are problems in our band bigger than not drinking enough Gatorade."

The subsequent hiatus, and the announcement of a retrospective five-CD set knowingly entitled The Collection Box, looked like a full stop. But here they are, with a sixth album Mechanical Bull, from which they drop two pats of fresh mechanical dung. The first, "Supersoaker", chimes and pounds in a radio-friendly way, but the second, "Always the Same (It Don't Matter)", built on a descending three-chord Stooges riff with some paint-blistering soloing from Matthew Followill, is cracking.

It's a shame that they're such insular cold fish onstage. Clad in more denim than Quo, they're more interested in face-to-face jamming than audience interaction, beyond the odd "You ready to have some fun?" or "You guys feel free to sing along", a flicked plectrum for the front row to fight over, and only some red lasers and white strobes to compensate for the personality deficit.

Not that London cares, bellowing heartily to the hits "Sex on Fire", "Use Somebody" and "The Bucket". No disasters, nothing to see here. Four guys turn up on time, play their songs competently, and everyone leaves happy. Where's the fun in that?

Critic's Choice

Laughing boy Leonard Cohen brings a lifetime mordant misery and dry wit to the 02, London ahead of regional UK dates in August and September. Meanwhile, bizarre South African "zef" rap-rave duo play The Ritz, Manchester (Fri) and Brixton Academy, London (Sat).