These seems like something that the two bandmates didn't rehearse, but it's fun nonetheless.
In a lot of cities that Metallica has played in, they try and do a song from a band that is from the city that they are playing in. They played Minneapolis, Minnesota last night, so Kirk Hammett with Robert Trujillo on vocals, ad-libbed their way through the Prince classic, "When Doves Cry."
They end up going into a "Let's Go Crazy" jam at the end.
I personally would have liked to have seen the full band do this with James Hetfield taking the lead, but it's fun in its own, off-the-cuff way.
Watch it below.