None of my friends wanted to come with me to the mid-July heavy metal symposium at the New Art Gallery in Walsall. The promise of a Friday evening spent listening to lectures on such topics as the Brummie origins of Black Sabbath and the history of grindcore (the extreme offshoot of metal invented in the 1980s by Napalm Death, if you were wondering) failed to attract them, for some reason. They missed out. Four decades after the words "heavy metal" were first used by the rock critic Lester Bangs to describe Black Sabbath, the West Midlands is rightly celebrating its place as the epicentre of a cultural movement that has swept the globe.
Heavy metal has long been sneered at by music snobs for being resolutely proletarian, often aggressive, and obsessed with macabre, occult imagery. Over its 40-year history, however, it has achieved a level of worldwide ubiquity rivalled only by that of hip-hop.
This year, the Indian band Parikrama were chosen to support Iron Maiden on two dates in their UK tour. Subir Malik, Parikrama's keyboard player and manager, tells me that heavy metal has "exploded" in popularity in India in the past five years. "Even though a minority of Indians speak English, people here connect to rock music like crazy," he says.
Metal also has a huge fan base in Latin America, where the Brazilian group Sepultura, in particular, have carved out a globally successful career by mixing fast and furious thrash metal with instrumentation and rhythms from Amazonian tribes. In Middle Eastern countries such as Iran and Egypt, metal is an illicit pleasure for teens who play gigs in each other's basements, away from the watchful eye of censorious authorities. Even in Jamaica, an island you might think would be saturated by reggae and its offshoots, there is a nascent hard-rock scene. The Jamaican novelist and former music journalist Marlon James explains the attraction: "Jamaican rock music is for kids who can afford their instruments. But it is also music for kids who are open-minded and diverse and who, having been exposed to the wider world, find reggae orthodoxy boring, restricting - almost the enemy. Reggae is to them what country music is to Americans: conservative, near right-wing and popular as ever with working-class Jamaicans. But it does not speak to them."
This explanation rings true for thousands of young people around the world: heavy metal speaks to them. And what does it say (apart from "Raaaargh")? At the Walsall symposium, a group of tattooed, T-shirted men gathered to discuss the question in earnest. Nic Bullen, a founder member of Napalm Death, described his band's low, guttural vocals as a form of "pure sound" that connects with listeners at a primal level. The music critic and artist Edwin Pouncey agreed, telling how, the first time he saw the ultra-noisy industrial metal band Swans play live: "It was like having the air pumped out of the room, so you could hardly breathe . . . It was scary, but the greatest feeling in the world." Pouncey later expounded on the attraction of heavy metal's grotesque imagery and lyrics, which draw from the "cesspool of human existence".
The Turner Prize-nominated artist Mark Titchner was there, too, to explain the influence that heavy metal has on his work. He did this by way of a dizzying animation, designed to replicate the feeling he first had on watching the Vertigo Records logo on his vinyl copy of Black Sabbath's 1971 album Master of Reality spin round and round on a turntable. The discussion opened up to questions from the floor. "Why do so many people hate heavy metal?" asked an audience member. This brought a blunt response from the musician and DJ Jon Pickering: "Because most of it is rubbish."
Nevertheless, in Britain heavy metal is more popular than ever. Last year, the rock mag Kerrang! became the country's biggest-selling music weekly, outselling its iconic rival New Musical Express by more than 10,000 each week. A new generation of pop bands such as Wolfmother is recycling the sounds of "classic" 1970s hard-rock acts, such as Led Zeppelin and Black Sabbath.
What does this sudden vogue for heavy metal mean for a subculture that thrives on its outsider status? Black Sabbath were roundly ignored by the music press when they started their career, and their debut album was turned down by 14 record labels on the trot before finding a release. It was only relentless touring that won the band fans, and in places considered off the map by the London-based media - Carlisle, Sheffield, Newcastle. As the genre grew in popularity, so did the proliferation of subgenres whose tentacles have crept under the surface of popular music: death, doom, drone, sludge, grind, speed, thrash, gore and countless more.
Metal's strong suit, and one that people who sneer at it tend to miss, is that it continually parodies itself. The leather-and-studs look, for example, was introduced by Rob Halford, the openly gay singer of Judas Priest, who simply nipped down to his local S&M shop when looking for a stage outfit, thereby transporting emblems of gay culture right into an ultra-macho environment. Metal fans are not stupid - they know there is a camp and theatrical element to the music.
It's not hard to see the appeal of yelling at the top of your lungs: it's an expression of rage, but also an expression of possibilities - dissatisfaction implies change, even hope. But why the West Midlands? For Bullen, the heavy metal sound is inextricably linked to Birmingham's industrial landscape. Napalm Death's music "reflected the culture we lived in, which was one of grey, concrete, brutalist architecture and ugly, vicious sounds. A lot of us came from the fringes of the city, from zones of boredom and alienation. That must feed back into the music somehow."
That concrete brutalism was symbolised by Birmingham's old Bullring shopping centre, which has now been demolished and replaced by a shiny new building. It is no less ugly, but the place speaks of a more affluent, multi-ethnic city. Perhaps as a result, heavy metal has been accorded a new status in the area's cultural heritage. On 6 July, the former Black Sabbath lead singer, Ozzy Osbourne, was honoured with the inaugural plaque on Birmingham's Hollywood-style Walk of Stars, prompting an outbreak of what local papers termed "Ozzymania". One parti cularly devoted fan had his name changed by deed poll to Ozzy Osbourne; city-centre bars and restaurants began serving bat-shaped burgers and "Prince of Darkness" cocktails.
The symposium at the Walsall art gallery was just one part of the SuperSonic festival, a weekend of underground rock music. Top of the bill this year was the drone band Sunn O))), whose avant-garde take on heavy metal was picked up on by the fine art world last year, leading to a performance at October's Frieze Art Fair in London.
Perhaps heavy metal has finally gained a degree of respectability - or has at least been rendered bland enough to fit neatly into consumer culture. Outside a city-centre branch of HMV, 12-year-old Priya, sporting a T-shirt that read "Made in Punjab", was standing with her family and laughing at the display of Babygros emblazoned with the logos of various metal bands. She said that at her school, being a heavy metal fan still marked you as an outsider.
"People are classed into different types - Goths, emos, grebos - and they say if you listen to heavy metal then you're one of those," she explained. "I don't agree. I like all types of music - I like Motörhead, Led Zeppelin and the Stranglers - and I don't think you should be classed as a certain type of person just because you listen to a certain kind of music."
Later, I cornered a long-haired, middle-aged Ozzy fan who looked nonplussed when I asked him about the accolade recently bestowed upon his hero. He knew well enough not to trust the vagaries of fashion, and with good reason: the metal-inspired designs at a nearby branch of Topshop were already making their way to the "£5 or less" bargain rack, shunted from the window display by the Day-Glo colours of "new rave", this year's must-have look. "Who's going to be next on the Walk of Stars? Jasper Carrott, probably," he said with a grimace.
Why I love metal
Mark Titchner, Turner Prize 2006-nominated artist
Music in all its forms has always provided a rich vein of reference and inspiration for me. It is of course a great, populist art form, but it is in its hinterlands and subgenres that
I have found its greatest influence on my practice as an artist.
This is what leads me particularly to metal. Of all the musical genres it is the most diverse, encompassing everything from the traditional technical and blues-based forms to abstract electronica without a hint of a distorted guitar or Marshall stack. Here are a few examples of how metal and the ideas have informed me:
Grindcore Napalm Death got me thinking about what happens when language ceases
to communicate meaning. Their moral standpoint as artists was also clearly analogous to the primal scream they produced, which leads us to the important realisation that music can contain sociopolitical messages without resorting to cliché.
Power metal Judas Priest, or rather the fear of Judas Priest, introduced me to the idea of subliminal communication.
Doom As well as pretty much creating the entire metal genre, Black Sabbath introduced me to op art, via their Vertigo label logo. They juxtaposed it with the existential terror of the void with their words and music.