Michael and Adam

“	Dean: Wait, Mic-- Michael lets you... talk? I mean, lets you be? Adam: Uh, yeah. In the Cage we came to an agreement. We only had each other.	”
	— Dean and Adam discuss his surprising relationship with the archangel. in Our Father, Who Aren't in Heaven

Adam (left) and Michael (right) in a diner after returning to Earth

Michael has a complicated relationship with his vessel Adam Milligan.

Background

The relationship between Michael and Adam Milligan is a complicated one right from the beginning. Needing the consent of Adam's half brother, his true vessel Dean Winchester, Michael arranged for Adam's resurrection from the dead as part of a plan to trick Dean into a situation where he would have to consent. Michael and the angels claimed that they would bring back Adam's mother in return, but it is unclear if they ever meant this. Adam was willing to consent to Michael to fight Lucifer, even though he was aware of the potential collateral damage the fight would cause. Adam is angered when he discovers the truth, but is trapped by Michael in the Green Room after the plan fails and is taken as a replacement vessel by Michael. Subsequently, Michael shows little care for Adam beyond a tool for his fight with Lucifer, coldly telling Dean that "Adam isn't home right now" when Dean addresses his brother in Stull Cemetery.

After being trapped in Lucifer's Cage together for years, Michael and Adam became all each other had and their relationship changed for the better. The two reached an understanding with each other and even appeared to have become friends, sharing control of Adam's body once they return to Earth. Both unsure of their place in the changed world after being gone for so long and sharing the fact that they possess complicated families, Adam and Michael have come to rely on each other as they adjust to their changed circumstances, choosing to remain together rather than going their separate ways now that they are free of Hell. The relationship is ended when God wipes out humanity, including Adam. Michael survives and continues using Adam's body as his vessel, but is noticeably saddened when informing the Winchesters of the news.

Season 5

In Point of No Return, Michael has Adam resurrected by Zachariah as part of a plan to manipulate Dean into saying "yes" to the archangel. After being offered the resurrection of his mother in return, Adam agrees to the deal. Adam refuses to listen to his half-brothers attempts to talk Adam out of saying "yes" and gives Zachariah his location in a dream when the angel visits him to remind Adam of their deal. However, Zachariah later reveals to Adam the truth that they were just using him to get to Dean, angering Adam. After Dean kills Zachariah and tries to flee with Sam and Adam, the descending Michael locks Adam in the Green Room with him.

In Two Minutes to Midnight, Castiel reveals that Michael took Adam as his vessel following his last failure to get Dean's consent.

In Swan Song, Dean attempts to apologize to Adam while confronting Michael in Stull Cemetery. Michael simply sees Dean as no longer important since he has Adam now and coldly tells Dean that "Adam isn't home right now," showing no care for his vessel.

Season 15

In Our Father, Who Aren't in Heaven, following their time in Lucifer's Cage and their escape from it, Michael and Adam are shown to have a vastly different relationship, one that is unusual for an angel and their vessel. Having been all each other had for close to a decade locked in the Cage in Hell, the two have reached an understanding with each other and even appear to have become friends. Michael now shares control of Adam's body with his vessel and rather than retreating into the background, manifests himself in the waking world to Adam to hold conversations with him. Their bond is heightened by the fact that they are both adrift in a changed world that they are unsure of their place in and Michael states at one point that he sees Adam as his guide on Earth.

Michael and Adam talking with each other.

After being captured by the Winchesters and Castiel, Michael is shown to be protective towards Adam and his anger at Dean specifically is over the fact that Dean abandoned Adam in the Cage while allowing Lucifer to walk free once again. After being given control, Adam briefly explains how he and Michael have reached an understanding during their time in the Cage and sides with his brothers against Michael on the threat from God. Adam is shown to be able to argue with Michael fearlessly which the archangel responds to with sincerity, despite his anger at the situation. Michael is reluctant to believe Adam over his father, stating at one point that he and Adam have only been together for years while Michael was with God for eternity. Adam is eventually able to get Michael to open up and admit that Michael feels that doubting God would be betraying everything that he has believed in and been his entire existence. Later, on Dean's request, Michael instantly relinquishes control to Adam so Dean can apologize to his brother despite his shown anger towards the hunter for abandoning Adam.

In Inherit the Earth, Michael reveals that God killed Adam along with the rest of humanity. Michael, still using Adam's body as his vessel, is noticeably upset when informing the Winchesters and Jack of this development and even states that Adam is gone "sadly."

Trivia

• Adam being possessed mirrors that of Sam and Dean's possession by Lucifer and the Alternate Michael.
  • However, Michael routinely allows Adam to have shared control of his body unlike with his brothers' possession where they fought against their possessor.