The film begins 6 months after the first public appearance of Superman:
CLARK KENT lives in Hobb’s Bay, writing at the Daily Star for GEORGE TAYLOR, an old friend of MARTHA and JONATHAN KENT.
To the public, Superman is still seen as a mysterious vigilant protecting the downtrodden of Metropolis. As a reporter, Clark gives a voice to the voiceless and shines a light on corruption. His latest takedown—GLEN GLENMORGAN, head of the city's second-largest company Galaxy Inc. Clark’s reporting connects the Galaxy Inc-sponsored high speed monorail project to numerous criminal charges ranging from poor working conditions to bribery and extortion.
The opening action sequence features Superman (wearing blue jeans and a t-shirt, with a bulletproof cape he was swaddled in when he arrived on Earth) confronting Glenmorgan and his goons while the police, headed by LT. DAN TURPIN, pursue.
Glenmorgan is forced to confess his crimes in front of the police after Superman drops him off the building. However, Glenmorgan avoids arrest when he later appears on television to call Superman an alien and a danger to society, which helps turn public opinion against the hero.
Clark has dreams about Krypton—fragmented flashes and bursts of color. It was a vibrant, thriving society….
Turpin and the police investigate Clark at his apartment after Glenmorgan was assaulted by Superman but Clark talks his way out of being a suspect.
We meet his landlord, MRS. NYXLY (a kooky character for now, whose 5th dimensional origins can be explored in a sequel or crossover event).
LOIS LANE works at rival newspaper Daily Planet with Clark’s best friend, photographer JIMMY OLSEN. The two try to get Clark to leave the Star but because Glenmorgan’s company owns the Daily Planet, Clark refuses. Lois and Clark have a competitive relationship, with the two always looking to beat each other to the story.
Meanwhile, Lois’s father GENERAL SAM LANE is working with LEX LUTHOR to capture Superman. It is revealed that the US government recovered Clark’s rocket after he landed as a baby, and have been using it for years to advance military scientific achievements. The ship’s operating system calls itself BRAINIAC.
The government is also developing a project using the Kryptonian technology co-opted by Luthor, General Lane, and young scientist JOHN HENRY IRONS called Project Steel Soldier. SGT. JOHN CORBEN is enlisted in the program and has trained for the last 5 years to pilot the experimental Metal-Zero/"Metal 0" suit. Corben has unrequited feelings for General Lane’s daughter, Lois.
Clark struggles to deal with the ramifications of Glenmorgan’s alien claims on the news, and the citizens begin to turn on him but he continues to investigate Glenmorgan.
It’s revealed that Clark's source is none other than Lex Luthor! In a private meet-up with Luthor’s assistant MERCY GRAVES, Clark learns that an Intergang terrorist attack on the monorail is imminent— Glenmorgan is desperate to destroy any evidence of malpractice amidst the growing allegations and cause a major tragedy to shift public attention.
Despite Clark’s warnings, Lois and Jimmy are aboard the monorail when the brakes are cut and Intergang terrorists strike. Lois organizes the people onboard to take down Intergang. Meanwhile, Superman manages to stop the runaway train but collapses from exhaustion.
He’s taken into military custody where he is interrogated and studied by Luthor and a team of scientists. Disgusted by their actions, John Henry Irons quits on the spot. Furthermore, we learn that the monorail derailment was orchestrated by Luthor as a way to lure Superman out for capture.
Lois shows up to confront her father with irrefutable evidence that Superman saved everyone on the monorail. As the two argue, Corben tries to jump in to speak with Lois but she’s more interested in Superman.
Meanwhile, Superman breaks frees (he just needed time to regain his strength) and fights his way through the military facility where he eventually finds his rocket ship and escapes with it.
Clark returns to Smallville to inspect the rocket ship with his parents who confirm it’s the same one from the night they found him. He’s able to “activate" it and holographic images appear-- digital memories of his parents JOR-EL and LARA that he recognizes from his dreams. Later, Martha helps him create his classic suit from materials inside the rocket.
After seeing Superman in action, and how Lois sided with him, Corben urges General Lane to fast-track Project Steel Soldier and volunteers to be the first pilot. In a procedure overseen by DR. EMMETT VALE, Corben fuses with the Metal-Zero suit. As he becomes METALLO, his heart bursts but he still manages to survive the process with his mind and body now corrupted by Brainiac who reveals its master plan to General Lane and Luthor:
Brainiac is a cosmic collector, responsible for the destruction of Krypton and countless other worlds. It corrupted Krypton’s infrastructure where it first received its name Brainiac. On Earth, it was called the Internet. With Metallo and the army of METAL MEN created for Project Steel Soldier thanks to Lex Luthor’s ingenuity, Brainiac will prepare the Earth for its final preservation before its destruction (sequel bait).
Major weapons systems across the globe are shut down while mundane machines with Internet access transform into Metal Men and begin collecting valuable artifacts like the Mona Lisa, keeping people in their homes, etc. (think the climax from I, Robot).
Superman turns to John Henry, who wears a prototype STEEL suit that he designed in secret, and the two face against Metallo and the Metal Men to save Metropolis, and the world!
In the end, Luthor threatens to destroy the world, knowing that Brainiac cannot allow Earth to be destroyed before it can upload all its history and culture. It’s a risky gamble but buys Superman enough time to upload a virus created by Dr. Irons to expel Brainiac’s influence on Metallo (and the internet), and save Earth…for now. Metallo surrenders to the US government and is placed in stasis until they can figure out a way to save him.
Later, Clark Kent joins Lois and Jimmy at the Daily Planet with Glenmorgan now arrested and charged. It’s revealed that this was all part of Luthor’s plan—give Clark information (some of which he planted / orchestrated himself) to help takedown his biggest business rival and let him take the fall so that Luthor’s company LexCorp can amass more power and influence.
As the film concludes, Superman holds a conference in front of the gathered press at Centennial Park where he introduces himself formally to the world.
END
In a mid-credit sequence, VRIL DOX is shown inside his classic SKULL SHIP somewhere out in the cosmos. He sets course for Earth…
