James Gunn is teasing a heroic turn for Lex Luthor in the upcoming film "Man of Tomorrow", which is described as a Superman story filled with hope, heroism, and spectacle. The film may feature a team-up between Superman and Lex Luthor as they face off against Brainiac. Details about the project are emerging as filming begins, with James Gunn sharing glimpses into the story and its characters, including Lex Luthor's role.