Last night, country star Zach Bryan broke the record for the largest ticketed concert in U.S. history at Michigan Stadium, a.k.a. Midway through his set, he brought out John Mayer, who opened the show, to sit in on “Friend of the Devil” by the Grateful Dead, who previously held the same record for over 45 years. Watch John Mayer play “Friend of the Devil” by the Grateful Dead with Zach Bryan at the largest ticketed concert in U.S. history below. John Mayer, meanwhile is set to headline a few festivals over the next week, including Pilgrimage Music & Cultural Festival in Franklin, TN, Palm Tree Festival in Montecito, CA, and Rise Festival in Jean, NV. Zach Bryan With John Mayer – “Friend Of The Devil” – 9/27/25[Video: Chris]Zach Bryan With John Mayer – “Better Days” – 9/27/25[Video: Nunya]