Headliners: The Prodigy, Iron Maiden & Metallica Sonisphere is the festival that inspired me to write this list and for good reason: with constant innovations the introduction of comedians like Bill Bailey to headline a main stage at a major music festival to shocking line-up announcements Rammstein's first ever UK festival performance or Biffy Clyro to headline a 'metal' festival alongside Metallica and Slipknot Sonisphere is leading the way in catering to the fans. With a modest capacity ranging between 60,000 and 80,000 the festival never feels crowded or to dead, but for those that are there the atmosphere is something that puts other festivals to shame. Everyone is so upbeat and friendly all the time, and it's not the sort of place for pessimism to thrive. Sonisphere is my favourite festival. I've been to the three prior UK editions and loved every minute of it, and with this year being the 40th anniversary of rock festivals at Knebworth, there's a good chance we're in for a treat. Likelihood Of A Sell-Out: 4/10 After cancelling midway through promotion in 2012 before taking a year-off in 2013, Sonisphere has a long way to go to prove itself to fans again. I have no doubt the festival won't be amazing but in no way should you worry about tickets, even if the presence of Maiden and Metallica's "By Request" set-list should pull in a lot of willing rock fans.