All the Major Characters Who Return in Avengers: Endgame

Sam was snapped out of existence at the end of Infinity War, but it's his return in Endgame that alerts Cap that reinforcements are on the way. As Steve faces down Thanos, almost alone, he gets a call in his ear: Sam, with his callback line "On your left." Sam leads the army of returned characters through portals to finish the fight. And when an elderly Steve returns after his decades-long journey, it's Sam who gets the shield and, presumably, the mantle of the new Captain America.