In addition to the stacked bill of Def Leppard, Mötley Crüe, Poison and Joan Jett & the Blackhearts, the Stadium Tour also features an opening set from a young up-and-coming band called Classless Act.

Speaking with ABC Audio from the road, Classless Act vocalist Derek Day shares he’s been impressed by “how nice everyone’s been” and the professionalism of everybody on the tour, from the crew to the Crüe.

“The day we got in … [Poison’s] Bret Michaels and C.C. DeVille, within 40 minutes, they were just already hugging us and welcoming us,” Day says. “We got to talk to Nikki Sixx and all sorts of great people.”

The big headline from the Stadium Tour so far has been that Mötley drummer Tommy Lee is playing with broken ribs. Ozzy Osbourne drummer Tommy Clufetos has been subbing in for Lee whenever he needs to take a break.

For Day, watching Lee not only battle through the pain, but start to play more songs in the set as the tour goes on, has been “insane.”

“Now he’s just doing more and more and more, he’s getting better, stronger,” Day says. “Even in the beginning, he would finish the set, and then he would walk off stage and play cowbell to the rest of the songs he wasn’t playing. So he’s just got it in his heart, and it’s so cool to see.”

In addition to getting a firsthand lesson in the “no pain, no gain” of rock ‘n’ roll, the Classless Act members are learning how to play the biggest stages of their lives.

“We’re actually communicating with each other more,” Day says. “We’re looking at each other, and we’re hitting things better with each other.”

The Stadium Tour continues Thursday in Nashville.