While he did have a brief appearance in Batman v Superman: Dawn of Justice, Justice League will be the first time Victor Stone, AKA Cyborg, and Ray Fisher, the actor portraying him, are blessed with a proper big screen appearance. The footage shown at Comic-Con in 2016 gave fans a first look at Cyborg's design, but fans had yet to see him in action, making him one of the biggest question marks of the movie. Now that the teaser has shown us a fully armed and operational cyborg, fan concerns should certainly be assuaged - he looks amazing.
The clip is only a few seconds long, and a good chunk of it is footage we already saw in the Comic-Con footage, but it still gives us a good look at what to expect from the full trailer tomorrow as well as some hints about the movie itself. The fact that we see Victor Stone in civilian clothes both in his human form and as Cyborg suggests that the movie will contain more flashbacks of his origins, and shows that his transformation with the Mother Box is permanent.
The real juicy bit is that we finally get to see him in action, vaporizing falling debris with his sonic cannon before it hits some civilians. Considering both Man of Steel and Batman v Superman were criticized by some for not explicitly showing the heroes saving more lives, this inclusion could be a big boon leading into Justice League, stating clearly: "yes, these heroes protect the innocent."
The teaser also shows Cyborg on the Flying Fox as one of his arms transforms into another weapon. With rumors that he'll sport a full-on "battle mode", it'll be exciting to see just how much of an arsenal his body can pack thanks to the Mother Box.
Source: Warner Bros.