The movie picks up where the aforementioned Batman v. Superman left off. Superman is gone, having sacrificed himself to save the world. Meanwhile, Batman (Ben Affleck) and Wonder Woman (Gal Gadot) begin to recruit an alliance of super-duper people (Flash (Ezra Miller), Cyborg (Ray Fisher), Aquaman (Jason Momoa)) to prepare for what appears to be another alien threat.
That alien threat is one Steppenwolf (Ciaran Hinds), the nephew and second-in-command to the yet-unseen super big bad named Darkseid. Steppenwolf has arrived on Earth to collect three Mother boxes objects that, when joined together, will grant immense power, etc., etc., etc. Steppenwolf is aided by thousands and thousands of Parademons, bug-like creatures who were once men.
Here's a brief list of what I liked about the movie. 1) Bruce Wayne has a wry, understated sense of humor that get this is also self-deprecating. 2) Jason Momoa kills as a manly-man king of the seas. 3) Gal Gadot is just as terrific as she was in her own movie and in BvS. 4) The Flash is hilarious! 5) There were plenty of tight action sequences that, despite being shown in IMAX, were easy to track. I could see who was fighting whom and with what!
The overall tone of the movie is more in line with what Marvel's doing there's physical fighting, there are biting remarks, there are doubts (our heroes are human-ish, after all), there are touching moments. Everyone delivers, which isn't always the case in ensemble pictures, but Affleck in particular really stepped up his game as the Bat dude. A lot of people liked his performance in BvS, but I found him stiff and boring. That's just not true in Justice League. Bats still has a huge ego, still likes to run things, likes to work alone even among his team. And he's still kind of a jerk. But he's not a boring jerk; Affleck, finally, gives him a personality! And lo! DC was saved!