Machine Gun Kelly and Slipknot lead singer Corey Taylor got into a heated exchange on Twitter, Monday, regarding a verse Taylor provided for Kelly's album, Tickets To My Downfall, that went unused. Taylor kicked things off during a recent podcast interview, in which he called out artists who transition into rock later in their careers.

“I [hate] the artists who failed in one genre and decided to go rock, and I think he knows who he is," Taylor said.

Machine Gun Kelly, Corey Taylor
Jason Kempin / Getty Images

In response, Kelly posted several tweets on the matter.

"Very odd that when an artist talks shit, and i respond, i’m the bad guy," Kelly began the series of tweets. "Corey did a verse for a song on tickets to my downfall album, it was fucking terrible, so i didn’t use it. He got mad about it, and talked shit to a magazine about the same album he was almost on."

Taylor fired back by sharing an email exchange with Travis Barker, in which Kelly is quoted as praising Taylor's verse, but asking him to try something different in the second portion of it.

“I didn’t do the track because I don’t like when people try to ‘write’ for me. I said NO to THEM," Taylor explained.

Check out the Twitter exchange below, including the private emails posted by Taylor.