Look. Comic book events are inherently messy. They require a lot of background knowledge. They almost always have half a dozen tie-ins that aren't included in the main TPB. Lots of cities are destroyed. Characters breeze in and out and you go what the heck was that? Then you forget about it. And at the end there is some super cosmic thing that makes zero sense and then the status quo is changed as we know it.
But knowing and moving past all of that, Dark Nights: Metal is, at the end of the day, a FUN event. Scott Snyder and Capullo are back, capping off a story seeded in their New 52 Batman run that revolves all around, you guessed it, Metal (both literal and musical), and introduces a new existential crisis from what we learn is the "dark" multiverse.
One thing about Snyder is that he's a builder. From word puzzles, to animal facts, to multiverse maps, he always infuses his stories with an extreme level of detail in terms of plots and worldbuilding. It's part of what made the Court of Owls, Endgame, and his other Batman storylines so engrossing. If you liked his work there, chances are you like it here.
In addition, as a not so small bonus, this event pulls off the amazing feat of re-contextualizing one of the most frustrating, messy chapters in Batman's history, the Grant Morrison era. Some people love it, some hate it. I'm in between but skew toward the latter. Morrison's Batman was IMO a purposefully convoluted, James Joyce-ian mess centered around a demonic Bat-god named Barbatos who screwed with Batman through the ages. Here, Snyder takes that chaotic mess and imposes his own kind of order on it, giving Barbatos a place in the multiverse (or dark multiverse) and structuring an explanation around him. That's a nigh-impossible feat. So for that alone he has my respect.
Does this all make sense? Heck no. Did I follow every development with the universe vibrations and the thule and the thing and the metals. Not even close. But did I like seeing psychotic multiverse versions of Batman terrorize the world? Secondary characters like Detective Chimp get a bit more spotlight? Crazy Joker dragons and a twisted Carter Hall? You betcha.
Don't think too hard about this one, and you'll really enjoy it, I think.