He is the Head of the whole body of believers, called the Church. "IT" the body, Christ's Church is what Jesus came to build. He as the Master builder, the Chief Cornerstone, and we, the church, the body of the saints, are builders together with Him as we proclaim the gospel of the Kingdom of God.
Matthew 16:18 (KJV) And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it.
1 Corinthians 3:9-11 (KJV) For we are labourers together with God: ye are God's husbandry, ye are God's building. According to the grace of God which is given unto me, as a wise masterbuilder, I have laid the foundation, and another buildeth thereon. But let every man take heed how he buildeth thereupon. For other foundation can no man lay than that is laid, which is Jesus Christ.
The Church according to the Bible is called 'her' and 'she' by the saints because the Bible tells us we the body, saints, church are the bride of Christ.
FYI - The Bible is written to the Church, the body of saints, ecclesia, called out ones, the bride of Christ ect. regardless of when we are alive upon the earth. If the Bible is written only to the original audience alive at the time of writing it makes little sense for Christ to tell us to preach the Word unto all people that whosoever among the mass of humanity shall hear and believe shall be saved.