Although Scott Snyder describes DC's Dark Nights: Metal event as a "summer blockbuster," he describes the story's plot as "a really simple story."
"It's essentially, the Justice League discovers that there's a Dark Multiverse out there, and that Dark Multiverse is coming to invade," Snyder said. "And everybody is screwed."
The writer said the only thing that will stop the invasion is Nth Metal, the material that's been previously associated with Hawkman but is being incorporated by Snyder's Metal into the wider DC Universe.
"So they go around trying to find the stuff, this Nth Metal, which is one of the rarest things in the universe," Snyder said.
The plot details were revealed in a DC Entertainment video interview with Snyder during Day 2 of Comic-Con International. The Metal event is being promoted significantly by DC during the San Diego event.
Snyder said that at the beginning of Metal, the first wave of the Dark Multiverse's attack comes from "these crazy, evil, nightmare Batmen that are the Dark Knights."
"So, it's basically every kid toy I ever wanted to play with or build, and just smashed together over the summer," Snyder said.