My friend told me a bit of storyline for a paperback he read but doesn’t remember the title.
All I know is that it’s Batman and Superman against Mettallo. At one point Bats and Supes are stuck underground so Bat puts a grenade or something to Superman’s chest and hides behind to blast a way. They end up digging into the Batcave where Alfred is waiting there with a shotgun.
I know it’s not much to work with