@thegibson Was trying different motherboards in a metal ATX PC case to see which combo worked with the drive docks I wanted to use. Because I was impatient I didn't secure the board to the case and just let it sit on it, without even the standoffs in the way.
Then I turned the machine on, heard lots of beeping. Did a quick hard reset but it no longer booted.

No magic smoke, but that day I learned that metal is in fact a conductor, even when you can't see it touching. 🙃