Did Paul ever teach that Christ is the King of the church?
No. Paul never teaches that Christ is the King of the church. While Christ is King of kings and Lord of lords, Scripture says He is not King to the church; He is the head of the body. Paul consistently presents believers as members of Him, not subjects kowtowing to a king.
Les explains that it is not scripturally correct to refer to Christ as our King, even though He is the King of kings, Lord of lords, and the God of creation. To the church, He is not the King; He is the head of the body. Les draws the contrast: if Christ were our King, then believers would be subjects, but Paul never gives the illusion that we are subjects who must kowtow to His every command. Instead, believers are part of Him, just as the wife is part of the husband. The wife submits to headship, but not as to a king. Les says that if anyone can find where Paul teaches Christ is the King of the church, he invites them to show him, because he cannot find it. Paul constantly refers to Christ as the head of the body, connected to believers as members of the body of Christ.