This movie launched the Marvel Cinematic Universe, back in 2008. Don’t remember what happened? I’ve got you covered.

We start off with Tony Stark, Iron Man, taking a ride in a military convoy, cracking jokes. That doesn’t last long before they are attacked, and Iron Man comes face to face with a missile that literally has his name on it and the thing explodes in his face.

Flashback several hours to an award show to introduce the billionaire genius playboy that is our protagonist, the business partner Obi Stain that raised him and ran his company after his father’s death, and Colonel Rhodes, his friend and military liaison. After he seduces a reporter that scolded him for his weapon making we also meet loyal assistant Pepper Pots and Iron Man’s house AI Jarvis.

Cast introductions more or less complete Iron Man hops a flight to the middle east to show off his new super missile tech, leading him back to the caravan we already saw, and the aftermath where he’s taken captive by terrorists and forced to build his super missile for them. Iron Man is appalled to find his weapons in the hands of the terrorist group the Ten Rings, and pretends to build the missile for them while secretly making a weapon of his own, while also dealing with a significant injury from the previous explosion. He builds a small but powerful power source he puts in his chest to prevent shrapnel from destroying his heart and uses the extra energy to power his very first Iron Man armor suit, bust out of the facility, and blow up most of the stolen weapons. Unfortunately his cellmate and temporary assistant dies during his escape attempt. Also unfortunately the suit is mostly destroyed and abandoned in the desert as Iron Man wanders off to be rescued.

Returning home Iron Man announces that his company will no longer make weapons, and he sits down to try to improve on his suit design. He upgrades the power unit in his chest, has a test flight where the suit freezes up, fixes the issue, and ends up with the more or less standard design he will use going forward. While the suit is building he heads to a party and finds out that Obi has been making deals with the terrorists behind his back, and that more weapons have fallen into their hands, including the dreaded missile.

Fueled with resolve, Iron Man takes off for the middle east for a test drive of his new suit weapon, and takes out the weapons and a terrorist cell, though he also has a run-in with the US military. Meanwhile, now having a demonstration of the power the suit offers, the terrorists have retrieved the prototype from the desert and offer it to Obi, who starts to build one of his own.

After his victory Iron Man wants to know who else Obi secretly sold weapons to, so he sends Pepper out on an espionage mission, and she discovers that Obi actually paid the terrorists to kill Iron Man in the first place, to get him out of the company and out of the spotlight. Before she can warn Iron Man, Obi shows up and paralyses him to steal the power source so he can power his own suit, leaving Iron Man to die. Once the paralysis wears off he is barely able to make his way downstairs to retrieve his old power source to save his life before passing out.

At this point everyone is in a rush. Pepper sends Rhody to check on Iron Man before heading to the lab with some government agents to detain Obi. They are unfortunately too late, the suit is complete and Obi takes on the new identity of the Ironmonger and attacks. Fortunately Rhodes has revived Iron Man, and even with low power he flies into action and takes on Ironmonger. He buys some time by tricking him into flying to high and freezing, but ultimately Pepper has to blow up the facility to take him out, which Iron Man barely survives. In the aftermath they have a press conference and the agents concoct a cover story for Iron Man to hide his identity, but he’s too proud from finally doing something worthwhile and tells the world he is now a superhero.

After the credits roll we get a teaser in the introduction of Nick Fury, who approaches Iron Man about joining the Avenger’s initiative.

TLDR: Rich genius builds a weaponized flying suit and becomes a superhero after his weapons get into the wrong hands. Mentor betrays him and must be stopped.