In Ephesians 5, Paul speaks towards marriage being like Christ and the church (the body-Gentiles).
In verses 28-32, Paul writes, "So husbands ought also to love their own wives as their own bodies. He who loves his own wife loves himself; for no one ever hated his own flesh, but nourishes and cherishes it, just as Christ also does the church, because we are members of His body. FOR THIS REASON A MAN SHALL LEAVE HIS FATHER AND MOTHER AND SHALL BE JOINED TO HIS WIFE, AND THE TWO SHALL BECOME ONE FLESH. This mystery is great; but I am speaking with reference to Christ and the church."
A huge discovery here is that God desires husband and wife to love each other in the same way that they love themselves. When in union with Christ, the self includes (the love for) Christ as the union with Christ is one flesh already. Therefore, the foundation of the marriage between husband and wife is built upon the marriage between a believer and Christ, hence the term, in Christ.
In the total, intense fusion of body, emotion, and spirit, of the sexual experience we are connecting with what it can be like to be totally one with God. As we enter into the "total being" experience of climax, we are released from all control as the mystical union of two bodies create the closest merger of body and spirit. As we are in union with Christ, the more we release control, the greater the feeling of merger between body and spirit. Awesome! :-)