It is a sequel to Wajda's 1976 film Man of Marble. That film told the story of Mateusz Birkut (Jerzy Radziwiłowicz), a campaigner for worker's rights who had once been a hero of Communist Poland but had become an Un-person due to his activism and clashes with the government. It ended with Birkit's son Maciej Tomczyk (also played by Jerzy Radziwiłowicz) telling documentarian Agnieszka (Krystyna Janda) that his father had been dead for years.
Man of Iron picks up the story of the son, Tomczyk (Jerzy Radziwiłowicz). It is 1980, and Tomczyk is a leader of the Solidarity trade union. Solidarity has risen up and gone on strike, shutting down the Lenin Shipyard, crucial to the Polish economy. The Communist government wishes to crush Solidarity but also wants to avoid the violence and death caused by government repression of the protest movements of 1970 and 1976. So they recruit Winkel, a producer for Polish radio, and give him a mission. Winkel is to infiltrate the Solidarity movement by pretending to make an admiring documentary on Tomczyk. His real goal is to dig up dirt on Tomczyk that the government will use to discredit him and, by proxy, discredit the Solidarity movement. He interviews many key people in Tomczyk's life, including Agnieszka—now Tomczyk's wife (Krystyna Janda reprises her role as well.)
Man of Iron was made during the brief thaw in Polish Communist rule between the August 1980 agreement in which the government legalized Solidarity, and the December 1981 crackdown in which the authorities imposed martial law on Poland and banned Solidarity again.
- The Alcoholic: Winkel starts to get the shakes after going too long without alcohol, as the strike at the shipyard has interrupted the shipping of vodka into Poland.
- Alone in a Crowd: Winkel is thrown out of Solidarity headquarters, the movement having discovered that he was sent to infiltrate them by the government. He walks out in a daze, alone in the triumphal crowd of people leaving the shipyard after the Gdansk agreement was signed.
- As Himself: Lech Wałęsa, leader of Solidarity and future President of Poland, pops up a couple of times as himself, as does Anna Walentynowicz, another hero of the Solidarity movement—they're both witnesses to Tomczyk and Agnieszka's wedding. Communist politician Jerzy Borowczak also appears as himself.
- Based on a True Story: Opens with a disclaimer saying "The people in this film are all imaginary but the situations are real and use has been made of documentary material." Stock Footage is in fact interspersed throughout the film, and the people aren't all imaginary, since Lech Walesa appears as himself.
- Bittersweet Ending: The workers have won recognition of Solidarity, but Winkel is left alone, having burned his bridges with the government and then being rejected by Solidarity for being a spy. And there's also the ominous warning from the commie bureaucrat who hired Winkel, who tells him that the agreement is worthless, signed by the government under duress, and that the government will revoke it at some future date. (This was very prescient on the part of Wajda, as the government did revoke the agreement and ban Solidarity just a couple of months after this film was released. The real Happy Ending didn't come until after the revolutions of 1989 led to the end of communism and the liberation of Poland.)
- Calling the Old Man Out: Tomczyk the callow young student in 1968 calls out his father for not rallying the workers to support the student protests. As it turns out, his father was right, but Tomczyk later refuses to bring out the students to support his father and the workers in 1970—see My Greatest Failure below.
- Commie Land: A portrait of Communist repression and popular resistance made during a brief thaw in said repression in Poland.
- Cut Phone Lines: Winkel, sent to Gdansk, attempts to call back to Warsaw but finds out that the telephone lines to the capital have been cut. (In Real Life the government did this over the whole country when imposing martial law not long after this film was released.)
- Framing Device: The film starts in 1980 with Tomczyk as a leader of the Lenin Shipyard strike. We then see his life story from 1968 to 1980 as a series of flashbacks, framed by Winkel interviewing various people related to Tomczyk—his friends, his grandmother, Agnes.
- Grave-Marking Scene: Tomczyk, denied a grave for his father after the authorities disposed of the body to parts unknown, puts up a cross at the spot where his father was shot down on the bridge. The film ends with him visiting the spot again and promising that the workers will win.
- Identical Grandson: As he previously did in Man of Marble, Jerzy Radziwiłowicz plays both father Mateusz and his son Maciej.
- My Greatest Failure: Tomczyk, bitter over his father and the other workers refusing to support their protests in 1968, refuses to bring out the students to support the workers when the workers are protesting in 1970. His father is killed in the protests. Tomczyk later regards this moment with shame, dropping out of school to work in the shipyard, citing his own failure when attempting to rally workers, and repeatedly visiting the spot where his father died.
- Off-into-the-Distance Ending: Ends with Tomczyk and Agnes walking across the bridge where his father was killed, after Tomczyk has paid his respects at the site and promised the workers will win in the end.
- Overly Nervous Flop Sweat: Winkel the sad alcoholic failure is often shown to be very sweaty, especially when he's talking to his Communist bosses.
- Reality Has No Subtitles: There are snatches of French and Russian dialogue that aren't subtitled. When a sympathetic doctor reads out the Russian-language diagnosis of Tomczyk as he's being released from the nut house, his friend Dzidek asks if she can translate it. The doctor says "What's the point? We kept him long enough, didn't we?"
- State Sec: They're everywhere in Communist Poland. They recruit Winkel, they occasionally chuck Tomczyk in jail, and in one scene they're shown ransacking Tomczyk and Agnieszka's apartment.
- Sudden Downer Ending: For Winkel, anyway. Immediately after he's quit his job, telling his commie bosses back in Warsaw to screw off, he's cast out by the Solidarity leadership. He was ratted out by those same commie bosses.
- Supporting Protagonist: Notionally, the protagonist of the story is Tomczyk, who succeeds his father as a labor leader and anti-government crusader; the series of flashbacks tells his story. But the real protagonist is Winkel the radio journalist. He starts out as a jaded, sad sack alcoholic, but finds inspiration and rebirth in the movement that he was supposed to help crush.
- Take This Job and Shove It: Winkel, inspired by the people he has met in the Solidarity movement, calls back to the office and quits his job.
- Title Drop: Maciek's grandmother observes that while his father was a ready-made hero, "Maciek had to be hammered out, like a piece of iron."
- Train-Station Goodbye: A tearful one between Tomczyk and Agnes as the State Sec raid on their apartment leads Agnes to take the baby and go to a safer place with her family in the country.