Mayhem Fest wrapped up its existence in 2015, and as of 2019 announced they'd be coming back this year. No word on what to expect from the festival surfaced at the time, but now we're starting to hear rumors. Blabbermouth reports Megadeth and Lamb Of God may very well the first Mayhem Fest in five years. This would be Megadeth's first since 2011 and Lamb Of God's first since 2010.
Megadeth and Lamb Of God headlining a summer North American tour also makes perfect sense. Megadeth is trying to put out new music this year, and Lamb Of God has explicitly started teasing that they're working on a new record.
Of course these Mayhem Fest appearances should be treated as rumors for the time being.