“None of it makes sense,” says Oli Sykes. “But nothing in life makes sense to me.”

It’s a reasonable way for anyone to think after everything that’s happened in 2016. But it’s maybe inevitable when you’re the singer of Bring Me The Horizon, a metal band that not long ago were playing to tiny clubs and are about to play two nights at the O2 Arena.

And that’s just the latest apparent absurdity for a band to whom each achievement seems to come as a welcome surprise. Bring Me The Horizon released their fifth album, That’s The Spirit, in late 2015; its poppier sound launched the band to critical acclaim and an almost number one album. Then the group played the Royal Albert Hall with an orchestra and a choir. The band look dangerously close to becoming rockstars, bringing metal to audiences of a size not seen in the UK since the 1980s.

“We’re kind of just always playing catchup with what’s being asked of us," Sykes told The Independent. “It’s not like we’re trying to get big,” he said, describing how it just seemed to be that the band were being asked to do bigger and bigger things, playing to more and more people.

Oliver Sykes of 'Bring Me The Horizon' performs on the Other Stage during the Glastonbury Festival at Worthy Farm, Pilton on June 24, 2016 in Glastonbury, England (Ian Gavan/Getty Images)

“Everything’s just like mental. Nothing has become normal.”

And taking on the O2 – which kicks off an arena tour that sees the band play hometown venue Sheffield Arena, where Sykes had just watched Justin Bieber – feels just the same.

“We don’t really feel like an arena band,” Sykes says. “We’ll hopefully feel like one once we’ve played it.”

Sykes spoke to The Independent fresh from preparing for the tour. He hadn’t actually been to the O2 but described just seeing the stage and imagining the space it would need to be fit as “definitely scary”.

As it is he found it hard to imagine what the tour might be like. “It’s weird cause it’s just - I never know how I’m gonna feel for it,” he says. “I have to stand in the venue.”

But that same terror – and the excitement that’s the ultimate reason it exists – is central to what has kept the band going. Once it stops being scary, it stops being exciting; when that happens, there isn’t much point in carrying on, says Sykes.

“As soon as it doesn’t become exciting – it’s like when people skydive and are asked ‘Were you scared?’ If I weren’t scared what’s the point in doing it? You do it for the thrill.

“As soon as you stop appreciating it, it’s become just a job. The show is our skydive.”

Oliver Sykes of 'Bring Me The Horizon' performs on the Other Stage during the Glastonbury Festival at Worthy Farm, Pilton on June 24, 2016 in Glastonbury, England (Ian Gavan/Getty Images)

That isn’t just theoretical for Bring Me The Horizon. Sykes knows how close failure is, and how easy it might be for everything to fall apart. Other bands have done the same – but so, almost, did his.

“What happens is everyone becomes disconnected in the band, it’s easy for that to happen,” he says, looking at other bands that have burnt brightly and then burnt out. “As the shows get bigger and people get more distanced from each other, doing side projects and becoming a bit disconnected as a band. “That’s what was happening with our band a couple of years ago.”

Solace and salvation came in the strangest of places. Sykes has been public about his drug addiction – speaking candidly about it and his recovery at an awards ceremony in 2014 – and getting through that showed him and the band how precarious, and how important, everything is.

“The addiction to drugs and going to rehab was a blessing in disguise - it really reset everything for us,” he says. “The music’s the most important thing now, not the drugs.

“It’s a reset button - that reset button really showed us that we’re not indestructible. All this could be taken away from us so easily.”

Sykes realises how that might seem. But it can be seen in the band’s success – it wasn’t a coincidence, it seems, that it was an award for Sempiternal that Sykes chose to announce that he had been in rehab and was now recovering.

“It sounds kind of stupid to say me having a problem with drugs is the reason why we’re big now,” he says. “But it makes you see what’s important: we pulled our socks up and we dug our heels in. We really, really worked at what we did.

“We wanted to make sure we weren’t going to lose our place in it.”

But if that hunger was born in adversity, can it last? It might be obvious where you need to climb to when you’re at your lowest; but it’s different once you’re on top of the world. How, essentially, do Oli Sykes and Bring Me The Horizon avoid becoming Metallica?

“Anything’s possible,” he says. “The hunger really creates itself; you don’t have to.

“I don’t feel myself having to get motivated.”

As long as the band is surprised by its success, it seems, it can keep being successful.

Playing the O2 “feels like, oh god this is really serious – a lot of people like our band,” he says. “We’re always a bit pessimistic – I’ve always felt like we’re just fluking it.”

They've still got plenty to keep pushing towards – the arena tour isn’t the end.

“We were just a metal band at one point. We were doing alright and playing some shows and now… now we’re one of the biggest heavy rock bands in the world.

“We want more now. It’s no longer just a fantasy; people know who we are. This can go as far as we want want it to go. The only limit is us.”

For all the success that time and the band’s gradual change have brought, though, there have been complaints. The band’s sound has gradually moved from extreme deathcore to the much poppier mixture of styles that it has today – bringing arenas full of new fans, but turning some old ones dissatisfied at the same time. The band don't play their old songs much any more

Sykes recognises the change, but rejects the idea that it has altered anything fundamental. “We still feel like the same people,” he says. “I don’t think we’ll ever feel like rockstars.”

Part of what keeps the band grounded, he says, is that they haven’t yet reached the kind of stardom where your life becomes unliveable in any normal kind of way. “We just feel like ordinary people doing extraordinary things.”

And after this truly extraordinary run of shows – which will see Bring Me The Horizon hit the biggest venues that the UK has to offer - they’re going to get back to that ordinary life. The band will take a long break, he says, and just have a sit down.

“The world needs a break from Bring Me The Horizon for a year or so, and we can go and have some downtime.” The band will take a break – “it’ll be nice to have a bit of a normal life” and “sit at home for more than three days”, Sykes says – and pause their plan to continue taking over the world.

Sykes doesn’t seem like a man who takes downtime – the band has been moving “relentlessly”, he says, and it’s hard to imagine that coming to a stop. And, of course, he won’t.

Oliver Sykes of 'Bring Me The Horizon' performs on the Other Stage during the Glastonbury Festival at Worthy Farm, Pilton on June 24, 2016 in Glastonbury, England (Ian Gavan/Getty Images)

Sykes’ clothing line, Drop Dead, has “some exciting collaborations and projects” that it’s working on. Those new release will be the “biggest things ever” for the brand and so during the downtime he’ll get some time to focus on that.

For now the band is working on the tour, and taking nothing for granted on the way. The slow and gradual growth of the band – Bring Me The Horizon’s success came out of nowhere, in one sense, but the band didn’t – has meant that they know where they’ve come from and where they’re going.

“We’ve gradually built our thing up and we’ve experienced what it means to be a band,” Sykes says. That’s gone in a long chain of gradually growing things: “getting the bus to shows - getting your parents to pick you up - to driving a van - getting a tourbus - then getting planes - now we’re finally getting to go business class.

“We’ve experienced every single detail of what it means to be a band, it’s been building and building.”

And now Bring Me The Horizon will find out what it means to be an arena band. At one point, we talked about exactly what that means to Sykes, who discusses the fact that he was recently watching Justin Bieber at Sheffield Arena but doesn’t have a sense of how big the O2 is.

The London venue where the band will kick off their tour on Halloween is much bigger than their hometown arena. And the seats are so steep that they seem to stretch into the sky, so high that you can’t really see them from the floor.