Sponge-headed Scienceman informed me that Pat Boone had done a heavy metal album in the 1990s. Even better, he has a copy of it, which he lent to me. It's called "In A Metal Mood" and has Pat in leathers, riding a motorcycle.It includes "No More Mr. Nice Guy."
It all starts out with reasonable promise, but then 20 seconds in, you realise that this is less of Deep Purple and heavy metal, and more of hot jazz from an earlier era. I expected to see Sammy Davis Jr. peek out and give a thumbs up. Good guitar solo just before the 2:30 mark, though.
The final song on the album, "Stairway to Heaven," was not so jarring, as it had always been one of those contrast, slowed-down songs that every heavy metal band had a couple of.