What does Ephesians 1:23 mean?

Paul concludes this chapter by referring to the church as Christ's body. This is a common metaphor, and relatively easy to apply. We are the "hands and feet" of Jesus in this world. We are meant to influence the people around us, caring for them and working for good. This means different Christians will have different talents, skills, and roles to fulfill in serving God on earth (1 Corinthians 12).

The second part of this verse, however, is much trickier to interpret: "the fullness of him who fills all in all." The most reasonable interpretation is that Christ fills, for Himself, the church with all blessings. This coordinates well with Ephesians 4:10–11, which also refers to Christ "fill[ing] all things." Christ doesn't need the church to be made complete, but God's plans do tie together all that the Father wills (Ephesians 1:10). The church, then, is something Christ makes full through His gift of all blessings.