Recently the visual effects on Batman v Superman: Dawn of Justice were completed and 3D creature artist (Sean Ray) had this to say:
"Batman v Superman is wrapped, one the best films I have worked on! My inner child is happy!" Sean Ray added. "I'm the biggest superman fan ever! So it was a dream to work on it! Looking forward to seeing it on the big screen in March! I can't wait!! Good job everyone who worked on it!"
When asked after if Doomsday was in the movie, Sean Ray said:
"Unfortunately Doomsday isn't in Batman v Superman. Maybe in a Man of Steel sequel or a Justice League movie maybe".
Now, there is a chance, that he said this to throw us off the scent. But let's face it, it most probably isn't a lie. So, that leaves the question, "Who is the villain (except Lex Luthor and KGBeast)?" I have three guesses. Let's begin.
Why it could be him:
1.) Superman cannot physically beat him alone, because Metallo has a kryptonite heart.
2.) Lex Luthor created Metallo in the comic books. This would work well, since Lex Luthor is still meant to be the main antagonist of the film, so the 'common threat' cannot overwhelm his character. It needs to be clear that at the end of the day, it was all Lex.
3.) Zack Snyder has stated that, before BvS happened, he had plans to do Man of Steel 2, which would have Metallo as the main antagonist.
Why it couldn't be him:
1.) Since the movie is titled, Batman v Superman, I doubt Superman would fight Wonder Woman. I also doubt that Metallo could fight Wonder Woman for longer than about three seconds. Look at this scene from the trailer:
Someone obviously hit Wonder Woman into the wall, and I doubt Metallo could do that. I also seriously doubt Metallo could cause this much damage:
And there are a bunch of other reason on why he isn't the threat that unites Batman and Superman and sparks the creation of the Justice League. So in short, METALLO ISN'T THE COMMON THREAT.
OK, hear me out. Here's why he could be the common threat:
1.) The synopsis for the movie says,
"A new threat quickly arises, putting mankind in greater danger than it's ever known before."
Straight away, we know it can't be Metallo, since he isn't a 'greater danger' than Zod was. But Darkseid is definitely more dangerous than Zod. He is capable if causing city-wide destruction.
2.) He is the same as Doomsday. I mean, except that he rules a planet full of parademons that he commands, and that he has Omega beams. But if we were talking about individual power levels, Doomsday would be a worthy opponent of Darkseid. So if we can accept Doomsday, why not Darkseid?
3.) Omega beams:
Those beams were not fired by Superman. One, because the whole point of Zod's death was to give a reason to why he doesn't kill. Two, because his beams look like this:
The beam sizes are different and also trailers are designed to deceive the audience. Who else do you know that shoots laser beams do you know? Bizzaro? He is the same level threat as Zod, or actually, lower than him, since Zod was intelligent. Also, using Bizzaro would literally be recycling Zod, the fight scenes would look extremely similar. Also, Superman killed Zod on his own, so why would he need help from a demigod and a batman to defeat a fucked-up version of him? Whoever the 'common threat' is, should unite the heroes and show Superman that even he alone can't save the world. Bizzaro wouldn't do that.
Why it's not him:
1.) Remember what I said about the common enemy not overwhelimg Lex Luthor? Well, Darkseid will definitely overwhelm Lex Luthor. He would overwhelm the whole film. A villain like Darkseid belongs in a Justice League movie. It's like having Bane as an antagonist in a Superman movie.
That's the only reason I need to say, DARKSEID IS NOT THE COMMON THREAT IN BATMAN V SUPERMAN
Why it could be him:
Lex/OS sounds a lot like Brainiac. Not as in his origins, but as in his powers. Lex Luthor could create an AI (mixed with Kryptonian tech?) to alert the world if there are aliens near us. The programme could go evil, build a physical body etc. Basically Ultron mixed with Skynet.
2.) This 'EMP' attack by Wonder Woman could be aimed at Brainiac.
3.) Zack Snyder has said that before BvS happened, they had plans to do Brainiac.
Why it could not be him:
1.) Like I said, he would resemble Ultron too much and that would cause fans to think they are just watching a Avengers 2 rip-off.
Out of my three guesses, I would say the most plausible would be Brainiac. But Kenton Slaughter had a better guess:
"OMAC. Can certainly shoot a beam like that, can certainly take on Superman, Batman and Wonder Woman, can definitely be controlled by Lex/OS, and can most certainly lead into a larger threat (hundreds of thousands of human-based, Brother Eye-controlled OMACs). The OMAC virus was created by LexCorp and the Department of Defense (USAMRIID?) to deal with metahumans, concealed within thousands of unaware civilians. Lex/OS could conceivably be the basis for Brother Eye, which in the Countdown to Infinite Crisis storyline monitored every single human being in a fashion similar to the "Machine" on Person of Interest (via tapped cell phones, hijacked webcams, security cameras, etc.) Suicide Squad is the SECOND film in the DCEU, ahead of Justice Leaguers, they chose to focus on metahumans, and Viola Davis is contracted for two other films (despite no Suicide Squad sequels being on the radar). Why? Methinks Suicide Squad directly ties into both BvS and Justice League via the perceived metahuman threat. These, and so many other reasons, are why I think a Lex-created and controlled Zod-based OMAC is the threat."
The common threat being OMACs does seem more plausible than any of my guesses, so nice thinking Kenton Slaughter!
But remember, Sean Ray could always be trolling us!