Agent Coulson works for Strategic Homeland Intervention, Enforcement and Logistics Division. He first appears in Iron Man, where he attempts to debrief Tony Stark about his captivity. He is later called upon by Pepper Potts to arrest Obadiah Stane after she discovers Stane's plot against Stark's life. Coulson and his agents are defeated by Stane but Coulson himself survives the attack. He later tries to assist Stark in covering up his secret identity as Iron Man.
[spoilers] Coulson was assigned by Director Fury to revive fallen Avengers and people with the Terrestrialized Alien Host Integrative T.I. project or Project T.A.H.I.T.I. Coulson used a thousand year old Kree corpse which is filled with fluids to revive people. However, a drug called GH-325 made six test subjects have harsh symptoms such as writing alien markings and psychosis. As a way to lessen the symptoms, Coulson ordered a memory machine to erase the test subjects lives and start anew. Coulson told Nick Fury to terminate T.A.H.I.T.I. [/spoilers]
In Iron Man 2, Coulson is assigned to watch over Stark. He assists Tony in his research by presenting him with research done by Howard Stark.
Coulson later appears in Thor, supervising the containment and examination of Thor's hammer. Thor's hammer was considered an 0-8-4 or an object of unknown origin. He confiscates Jane Foster's research in order to further SHIELD's goals. He observes Thor's attack on the facility, allowing him to reach the hammer, but is disappointed when Thor fails to retrieve it. He then holds Thor for questioning, but releases him and has him followed. After surviving the attack by the Destroyer, Coulson agrees to return Jane's research to her in exchange for Thor's pledge to help them protect the planet.
Coulson appears again in "Marvel's The Avengers". He informs Black Widow that her friend Clint Barton has been compromised and orders her to recruit Bruce Banner. Coulson himself goes to recruit Tony Stark, delivering him a copy of the Avengers dossier and requesting his assistance. Coulson accompanies Steve Rogers to the SHIELD Helicarrier. He confesses to Rogers that he is a big fan of Captain America, and asks that Rogers sign his vintage Captain America card collection. When Loki escapes from SHIELD confinement, Coulson attempts to stop him with a newly developed weapon, but he is stabbed by Loki before he can fire. As he lies dying, Coulson manages to get one shot off at Loki, knocking the god to the floor. Before he dies, Coulson tells his boss Nick Fury that he is content to die, knowing that the Avengers will now have somebody to avenge.
It is revealed that Coulson had become good friends with Pepper Potts, much to the surprise of Tony Stark. Coulson also had a romantic affair with a cellist named Audrey Nathan, who moved to Portland and ended the relationship. Before Coulson's death, Stark offered to fly him to Portland and attempt a reconciliation.
Coulson's death had a profound effect on both the Avengers and on his fellow SHIELD agents. His polite, understated manner had endeared him to each member of the Avengers team, and his death was a primary motivation for them to set aside their differences and avenge his loss.
[spoilers] Days later, Nick Fury ordered T.A.H.I.T.I. to revive Coulson because Fury considered Coulson an Avenger. Phil Coulson's corpse was sent to the Guest House which is a World War II hospital. The GH-325 helped revive Coulson but lost his will to live. To prevent Phil Coulson from suffering trauma, he was uploaded with a fake memory of himself in Tahiti by a machine which removes his skull cap and touches his brain.
In 2013, Coulson was unaware of T.A.H.I.T.I. until moments later, when Coulson was sent by Raina to a memory machine. Melinda May formed a team of herself, Coulson, Grant Ward, Leo Fitz, Jemma Simmons and Rising Tide hacker Skye. On their missions, they found a group called Centipede which has been experimenting people. Their leader, the Clairvoyant wanted the GH-325 and ordered Ian Quinn to shoot Skye. Coulson went to the Guest House and found the GH-325. In 2014, it has been revealed that HYDRA infiltrated SHIELD and destroyed SHIELD. Coulson defeated HYDRA's Centipede program. Nick Fury came across Coulson and gave Coulson the opportunity to rebuild SHIELD. Later, Coulson was writing alien markings as a symptom of GH-325. Coulson came across Sebastian Derik who was one of the T.A.H.I.T.I. patients who writes the markings. Coulson realizes that the markings are blueprints to a city. [/spoilers]