Despite its rebellious reputation, when it comes down to it the heavy metal universe is one bound by an intricate set of rules and traditions. And Icelandic upstarts Sign have already broken most of those, mainly through after-show sessions on the JD lasting well into the early hours.

But not any more - frontman Ragnar Zolberg, who formed the band while still in his early teens, recently gave booze the boot, decades before being due to wash-up in the sad-old-lush-drying-out chapter of every good metal biography. What’s more, he and his bandmates were not shy of playing, ahem, Doncaster Gay Pride in 2007.

It may not sit well with the macho leather and studs metallers who deserted Judas Priest in their droves after Rob Halford came out of the closet, but Doncaster was obviously appreciative, inviting the band back for another round this August. More recently Sign committed perhaps their greatest blasphemy by covering Iron Maiden’s ‘Run To The Hills’, a heavy metal hymn that only the foolish or very brave would dare meddle with.

However, the unlikely outcome of an approach that could have been lifted from a textbook on ruffling feathers has been the emergence of a gradual, grudging respect for Sign. Their years of hard slog around every pub, toilet venue or Mardi Gras festivity that would have them were rewarded this summer with a slot on the main stage at Download festival, held in Maiden’s spiritual home of Donnington. The controversial cover version meanwhile was recorded at the request of metal bible Kerrang! for a cover CD supplied with an issue that heaped praise on the band over a two-page spread.

“We’ve been surprised actually,” says Zolberg, “things just started to take off all of a sudden.”

He acknowledges the journey that has brought them to this point has been far from straightforward. Even when they’ve had some lucky breaks, supporting established icons like The Wildhearts and Skid Row on tour, Sign have found themselves working hard to win over the crowds.

“I think it’s always been hard for us to be next to some other band,” he says. “We’ve done great tours with The Wildhearts, Skid Row, Wednesday 13, but none of those bands are really in the same genre as we are.”

Attempting to pin Sign down to a genre would be a fruitless task, their music being often as contradictory as their methods in promoting it. Although Zolberg and co-conspirators - drummer Eagle, bassist Heimir, guitarist A.G and guitarist/keyboardist Aggi - may only be 20-nothing they can already boast a rich history, having recorded a string of Icelandic language albums before UK debut Thank God For Silence hit the shelves in 2006. The record’s unlikely fusion of Zolberg’s trademark hair metal falsetto vocals and shredding solos, with lush goth melodies and keyboard touches that HIM would love to borrow, plus some bombastic work by Sign’s heavyweight rhythm section, was followed late last year by a heavier, brooding opus, misleadingly titled The Hope.

The band’s stubborn refusal to be tied down to a familiar metal subheading could be attributed to the fact that, in the surrealist musical landscape of Iceland, a place rarely noted for its metal exports, Sign were able to develop almost completely alone, independent of any ‘scene’ and the constraints of conventions.

“The typical Icelandic sound sounds like nature somehow,” says Zolberg, “like Sigur Ros and Bjork. We’re influenced by a lot of American bands and back home our fans have always been younger kids, younger than we are. Everyone who is older than us, they don’t quite like the fact that someone younger than they is doing something. Back home there is a lot of jealously and negativity”. Hence why the band have so determinedly set their sights on Britain, touring relentlessly on these shores ever since the release of Thank God For Silence. Such achievement for such tender years is enough to make lesser mortals feel wholly inadequate, and Zolberg confirms he has now upped his game by cutting out the hard party lifestyle which was a running theme on that first UK release, in order to focus fully on putting on a mind-blowing show.

Though it may be difficult to believe, the benefits of clean living were apparently a regular talking point on Sign’s May tour with Wednesday 13, the former Murderdolls frontman having himself opted to kiss the bottle goodbye.

“It gets so tiring you know,” sighs Zolberg, “drinking a lot and all that shit, it gets exhausting. Wednesday talked about thinking the same thing, that once you stop drinking your focus becomes more pointed at the gig itself instead of the after party or whatever. It’s not hard if you know what you want to do and if you’re comfortable with it.

“If you’re struggling with trying to stay sober then going on the road to do a tour is probably the worst thing to do, because it is full of temptation. For me it’s easy to just ignore it and disappear when people start getting drunk.”

With that renewed focus Zolberg is now starting work on a third English language record, which with partying off the agenda is set to address some “more serious topics - it’s too early to say what yet because I haven’t got my mind around it.” But fans can rest assured it won’t be too much of a departure.

“It will be heavy. It’s like I wanted to gain as much self-awareness as I could and that was sort of a journey I took, a mental journey. It’s taken me to some dark places and to bright places as well. That’s also because we come from Iceland, it’s very dark over here”.

In the midst of a festival season schedule that takes them from major events like Download and a Whitesnake support at home in Reykjavik to, of course, Doncaster’s annual parade, Sign have booked a one-off show at Camden’s Purple Turtle, giving punters impressed by their numerous supporting turns the chance to see them on a more intimate stage, armed with a more extensive set list.

“Camden especially is one of my favourite, favourite places,” Zolberg says, when it’s put to him it’s a long way to come for a single show. “We now see people travelling hours and hours to come to the shows, people we’ve gotten to know through major support tours. It’s just really fun to have this core of people who you know are here for you”. If more minds are prepared to open to them, the metal world at large could soon be Sign’s for the taking.

Sign play The Purple Turtle on 19 August 2008.