Almost as interesting as the artists Sammy Hagar is collaborating with on his upcoming 'Sammy Hagar and Friends' album is the list of artists he couldn't find time to record with. One, Metallica's James Hetfield, turned down Hagar's invitation, but the Red Rocker says he understands why.

Hagar tells Rolling Stone that he had his friend Hetfield in mind for 'Knockdown Dragout,' but after running into Kid Rock, he asked him to record it instead. Later, Hagar extended an offer to Hetfield to take another, lesser role in the song. "He got back to me and said, quote-unquote, 'I'm completely flattered that you would want my sailor-assed voice on your record,'" Hagar said. "And then he said, 'But it isn't my style.' And I said, 'It's OK. I still love you, James.'

"I was cheating by sending him that song, because … if a Metallica fan would've heard this album and bought it because he was on there, they would be pissed off."

In addition to Kid Rock, country singers Ronnie Dunn and Toby Keith are on the album. So are Taj Mahal, Joe Satriani and Chad Smith (Hagar's Chickenfoot bandmates), Heart's Nancy Wilson and Journey's Neal Schon. Hagar called his duet with Wilson the best on the record. Hagar said he also couldn't find room or time for Kenny Chesney and Grace Potter.

Hagar's plan is to release the album on Sept. 24 and then promote it with some big shows in 2014. He'd love to play festivals, but he never gets invited to perform at events like Bonnaroo and Outer Lands. "Chickenfoot wanted those festivals so bad," he admitted to Rolling Stone. "[But there's] something weird about my image or something I've done to where they don't want me on those shows. I'm going to beg for festivals. I'll play them for free."

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