Michael and Adam

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 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, Adam and Michael have come to rely on each other as they adjust their changed circumstances.