Many people have become pop stars without possessing any relevant qualifications. They have carved out their own niches - jobs that enable them to hog the spotlight without the bothersome irrelevancies of singing, playing or writing songs. They are rock and pop's spare parts. Some have vanished into obscurity, such as Bob Markley, a millionaire who bankrolled 1960s psychedelicists the West Coast Pop Art Experimental Band on the condition that he could be their tambourine player. Others are legendary, including the Happy Mondays' dancer Bez and Public Enemy's scowling Professor Griff.

No figure, however, sums up the spare part more completely than the British MC. No one really seems to know where MCs came from, but by the early 1990s they were everywhere, ruining perfectly good records by bellowing inanities over the top of them. "Sounds of the DJ!" they would cry, imparting vital information to ravers who thought they were dancing to the military band of the Royal Scots Dragoon Guards.

Since the rise of garage, MCs have become stars in their own right, apparently without any corresponding improvement in what they do. With the exception of the Streets' Mike Skinner - whose style has more in common with the streetwise witticisms of the late Ian Dury than his garage peers - MCs' lyrics still tend to be embarrassingly gauche, as evidenced by the witless hectoring of So Solid Crew.

Under the circumstances, Dylan Mills seems an entirely unique figure. An 18-year-old MC, he has risen through the garage scene as a member of the Roll Deep Crew, an east London equivalent to So Solid. There, however, the similarity ends. On the evidence of Mills's debut album as Dizzee Rascal, he not only has something to say, he has the intellectual equipment to say it in a remarkably original way.

Before you get to the lyrics, however, there is the sound of the album to overcome. Mills allegedly honed his production style after being excluded from every school lesson other than music. Boy in da Corner certainly appears to have been born in isolation. It sounds like nothing else - which is surprising in a time when some people seem to think that rock and pop are trapped in a kind of terminal postmodernity, eternally doomed to borrow from the past.

Presumably, they haven't heard Boy in da Corner, which appears to borrow from nothing other than the terrifying sound inside Mills's head. Disjointed electronic pulses pass for rhythms. Above them lurch churning bass frequencies, disturbing choruses of muttering voices, clattering synthesisers that recall police sirens and arcade games, and, on forthcoming single Fix Up Look Sharp, bursts of rock guitar. In contrast to the macho swagger of most garage MCs, Mills delivers his rhymes in a frantic, panicked yelp. The overall effect is shocking and unsettling in the extreme.

Shocking and unsettling people may be the point. The lyrics of Boy in da Corner deal with teenage life on an east London council estate, a world of "blanks, skanks and street robbery... pregnant girls who ain't got no love, useless mans with no plans". There is much talk of stabbing and shooting - "We used to fight with kids from the other estates," says Mills on Brand New Day, "now eight millimetres settle debates" - and a distinctly queasy humour on display. I Luv U tackles the subject of underage sex with mordant wit: "Pregnant? What you talking about that for? 15? She's underage, that's raw."

Given that Mills himself was stabbed last week in garage holiday destination Ayia Napa, you suspect that Boy in da Corner is likely to send Kim Howells apoplectic with rage. If it does, however, he's not listening properly. So Solid Crew's lyrics are repugnant not because they talk about violence, but because they explicitly equate violence with success, threatening to "bring the gats" or "take you to the morgue" before bragging about their champagne lifestyle. By contrast, Boy in da Corner depicts a bleak world, devoid of aspiration: no one in their right minds would want to live there. When, on Hold Your Mouf, Mills delivers the album's most striking line - "I'm a problem for Anthony Blair" - it sounds less like thuggish boasting than a despairing statement of fact.

However, whether anybody will listen seems questionable. Both Dizzee Rascal's music and message are wildly unpalatable, and the British record-buying public is not currently renowned for wild risk-taking. If they ignore Boy in da Corner, however, they may well be ignoring the most original and exciting artist to emerge from dance music in a decade.