In Dark Nights: Metal #3, The Flash was last seen assisting Steel in getting Superman through the portal to the Dark Multiverse in hopes of rescuing Batman and stopping a full-blown incursion into Earth-0. In The Flash #33, Joshua Williamson not only skillfully walks the line between padding out those events and expanding upon them, but also manages to advance Scott Snyder's overall Metal story.
Howard Porter in turn gets the opportunity to render a couple of the evil Dark Knights, faithfully bringing Greg Capullo's designs to life and giving the characters some exposure outside of the very crowded main series, making this Metal tie-in an important chapter in the overall storyline.
Williamson and Porter start off the issue with a very familiar but energizing scene – that of Superman racing The Flash. But this isn't a typical example of the races DC Comics' speediest heroes have run for the last 50 years – the two aren't pitting themselves against each other, but are instead racing together to save the life of their colleague, and possibly the world. It's a tense twist on an otherwise comforting trope that carries with it the same dire sense of darkness that's been so pervasive in Metal. Throughout the sequence, Williamson brings readers up to speed, as well, narrating the events of Metal thus far to the point where anyone can easily enjoy the issue, even if they're otherwise unfamiliar with what's been happening in the event's main story.
Once Superman has crossed over to the Dark Multiverse – readers will need to read Metal #3 to learn exactly what happens once he gets there – Williamson turns his attention to the remaining members of the Justice League and their quest for whatever traces of Nth Metal they can locate with the intent of defeating the invading Dark Knights. What happens to the team during their quest turns out to be a critical next step in their involvement, making this issue a key tie-in to the series – and one that unfortunately might be passed on by fans because it's "only" a tie-in. The Flash's acknowledgment of Superman's heroic presence is a nice corollary to Snyder's own portrayal of the Man of Steel as a beacon of optimism as seen in "Metal" #3.
Porter gets his moment to excel when the Dark Knights arrive – only two as mentioned, and only briefly, but Porter's rendition of their grand entry authentically feels threatening. As story circumstance removes The Flash from the scene, the way is paved for Porter to depict several dark and disturbing vignettes that appear to involve alternate incarnations of the Scarlet Speedster – versions that are perhaps, and even likely, stemming from the Dark Universe. Porter's final pages put forth plenty more deliciously dark imagery involving the other members of the League, helping to sell anyone still sitting on the fence regarding Metal to take their own plunge into the Dark Multiverse.
Dealing more with the happenings in Metal than with any ongoing issues with Barry Allen, The Flash #33 serves as a sort of Dark Nights: Metal #3½, doing an admirable job of enhancing the story. Flash fans who haven't been paying attention might find themselves wanting to now.