Dutch metal outfit Within Temptation have been having some fun en route to celebrating their 15th anniversary. Over the last few months the band has been recording and posting a number of covers of popular songs and putting their stamp on the tracks.

The band told Metal Hammer, "We figured this would be a great occasion to do something special for [the fans]. It will be a musical adventure as we are covering songs that are very close to us, but also songs that are not close to us at all."

So far, the group have run the gamut from classic rock (The Who's 'Behind Blue Eyes') to alternative (Coldplay's 'Paradise,' Gotye's 'Somebody That I Used to Know,' Mumford & Sons' 'Little Lion Man,' Gnarls Barkley's 'Crazy') to pop (Bruno Mars' 'Grenade,' Enrique Iglesias' 'Dirty Dancer,' Lana Del Rey's 'Summertime Sadness,' OneRepublic's 'Apologize,' Swedish House Mafia's 'Don't You Worry Child,' David Guetta's 'Titanium,' Adele's 'Skyfall'). The covers were meant to get fans excited for the band's 15th anniversary concert, which took place in Antwerp, Belgium last month.

Not all of the track stay true to the original and we offer a few examples below. Check out the symphonic rockers adding some aggression to Bruno Mars' 'Grenade,' making Gnarls Barkley's 'Crazy' a haunting tune, stepping up the pace on Gotye's 'Somebody That I Used to Know,' and offering a more atmospheric take on Mumford & Sons' 'Little Lion Man.'

Watch Within Temptation Perform Bruno Mars' 'Grenade'

Listen to Within Temptation Covering Gnarls Barkley's 'Crazy'

Listen to Within Temptation Covering Gotye's 'Somebody That I Used to Know'

Listen to Within Temptation Covering Mumford & Sons' 'Little Lion Man'