The Arctic Monkeys frontman, who has been top of the bill twice with his band mates Matt Helders, Jamie Cook and Nick O'Malley, aren't impressed by the news that the heavy metal band will headline the Sunday this year.
Alex said: ''I heard all the rumours [that they would play]. I'm not sure it adds up. I know we'd buzz off it, but fundamentally could you have Metallica in the hippy nucleus?''
The first time the band played the event at Worthy Farm they hung out with Lily Allen but still got stuck in to enjoying the festival atmosphere.
He said: ''The first time we went to Glastonbury was when we played it. I did the Stone Circle thing. I was dressed as a crocodile, because Lily Allen had a load of fancy dress costumes. I remember wrestling James from Klaxons in the mud as the sun rose.''
The 28-year-old star, who hails from Yorkshire, claims his best piece of advice for anyone wanting to get the most out of a festival is to join a band and play themselves.
He added to Time Out magazine: ''I went to Leeds festival twice when I was about 16 and 17. The following year we were playing in a tent there - much better! We never really considered going to any festivals down south. It just seemed too far away.''
The season 7 premiere guests featured some cast members we haven't seen much of for a while.
This year's Rotterdam event was definitely one to remember.
New album 'Flower Boy' comes later this summer.