Well, there is a lot to wade through in Metal. Especially if you haven’t read Snyder and Capullo’s run on New 52 Batman (the “Court of Owls” arc, to which Metal is a long-delayed; and MUCh grander, follow-up). There are two rather dense prologue issues (The Forge and the Casting), both of which are kinda meh, and honestly didn’t really sell me on anything... they feature art by John Romita Jr., who is actually one of my favorite artists in comics, but I absolutely LOATHE the way he draws Batman. Not lithe or derailed enough... too blocky for the character, kind of like his equally off-base drawing of Spider-Man (characters he draws well include Thor, Daredevil, Superman, the Eternals, Hulk, etc.)
But... once Batman disappears from the whole thing (which happens near the end of Dark Nights: Metal #2 I think) and the tie-ins — single issues focusing on the various Dark Multiverse incarnations of Bats, how they came to be, andhow they were tracked down and recruited by the Batman Who Laughs (Joker-Batman) and his master, the dark cosmic deity Barbatos (basically Spectre-Batman, a creature older than time), it really gets good.
The issue that just came out for instance, Batman: The Drowned; is about the Batman/Awuaman character (who is a woman, so... kind of a Bat-Aqua-Man-Woman?) is just PHENOMENAL. A genuinely great story about a really intriguing character.
Ad next up is the Ares/Batman mashup, the Merciless. Then the Doomsday/Batman, the Devastator.
I think some of these characters might end up sticking around after Metal is over. The Drownedis VERY popular, and frankly it’s one of the best comics featuring Aquaman that I’ve ever read.
Anyhoo... you could probably skip the preludes and start with Dark Nights: Metal 1, and judt read the intro paragraph to catch up on those boring Romita-drawn issues.
But... Mister Miracle is really the best thing happening in DC right now. That and Action Comics, which is dealing with Mr. Oz, and swiftly moving toward the beginning of DOOMSDAY CLOCK, which is absolutely not something you’re going to want to miss.