And not just any cyborg! The guy who's actually named Cyborg! Because he's a cyborg. You can tell because half of his head is metal and he has a glowing red eyeball.
Variety reports that theater actor Ray Fisher has signed on to the Batman-Superman film as Victor Stone, the hero who eventually becomes partially robot parts, then aptly named Cyborg. With Batman and Wonder Woman to some extent already being introduced in the film, it's not expected that Fisher will have a large role. This is merely introducing Cyborg so that he can eventually be a founding member of the Justice League--as he is in DC's 2011 relaunch of the comics.
Fisher joins a cast that includes Henry Cavill as Superman, Ben Affleck as Batman, Gal Gadot as Wonder Woman, Jesse Eisenberg as Lex Luthor, Colm Meaney as Captain Boomerang, Coldplay's Chris Martin as "The Chief," and Johnny Depp as Dr. Transcendence.