When Steppenwolf and his Parademon army come to Earth in search of the three Mother Boxes, Batman and Wonder Woman will need help repelling the invasion. One of their allies will end up being someone who's being powered by one of those Mother Boxes: Victor Stone, a.k.a. Cyborg (played by Ray Fisher). Victor's transformation from broken human to cybernetic hero was shown in Batman v Superman: Dawn of Justice last year, but Justice League will pull back the curtain on Cyborg's past further by exploring his family life and why he and his father are not on great terms, among other things. According to Joe Morton, who plays Victor's father, Silas Stone:
With Cyborg, and with Silas Stone, you're getting sort of the outside story. You'll get to know them vis-a-vis the death of Cyborg's mother. You'll get to know what Silas did in terms of reconstructing his son. You'll get to know the angst that's sort of created between Silas and Victor, his son. So I would imagine in the same sort of ways you're going to get to know the other characters.
As Joe Morton (a.k.a. Miles Dyson in Terminator 2: Judgement Day) pointed out to GameSpot, Cyborg isn't as well known to people who don't read the comics, while Batman, Wonder Woman, Flash, Aquaman and Superman are pop culture staples in one form or another. So even though we'll be able to further explore Cyborg in his upcoming solo movie, Justice League is taking the opportunity to shed light on how the death of Victor Stone's mother affected him, how Victor went from athlete to superhero and how this transformation led to a divide between the two Stone men.
It hasn't been revealed yet how most of Victor Stone's body was destroyed in the DCEU, but just like in the comics, Silas Stone worked desperately to rebuild his son. After multiple failed attempts, he finally found the key in a Mother Box, a portable supercomputer from Apokolips. We still don't know how Silas obtained the Mother Box, but when it merged with Victor, it slowly built him a new artificial body and granted him amazing techno-abilities. However, unlike his Justice League teammates, Victor is unable to lead a normal life because he can't hide who he is from the public, which is presumably part of the reason why Victor is resentful towards his father when Justice League begins.
Despite their differences, Victor and Silas will have to come together in Justice League when Steppenwolf's invasion requires Cyborg to step out of the shadows and aid his fellow superheroes. With one Mother Box powering Cyborg and two others under the care of the Amazons and Atlanteans, respectively, it will be up to the Justice League to stop Steppenwolf and prevent him from destroying Earth and leaving with these supercomputers.
You can see Cyborg in action when Justice League is released on November 17. The Cyborg solo movie is still scheduled for 2020.
