Is the marriage relationship between Christ and the church sexual?
No. The marriage relationship between Christ and the church is not sexual. Paul teaches that Christ is the groom and the church is the bride, but this union is merely positional and spiritual, not physical or sexual, because sexual matters will pass off the scene.
Les explains that Paul's teaching about Christ as groom and the church as bride is a positional relationship, not a sexual one. He stresses that it is merely positional and certainly not sexual, because the sexual aspect will pass off the scene. In I Corinthians 6, Paul had just asked believers whether they had no right to be joined to a harlot, and he clarified that this extends beyond a professional prostitute to any sexuality outside God's bounds. Verse 17 contrasts that with being joined to the Lord as one spirit. Les also notes Paul uses the marriage relationship analogy again in Romans 7:4.
But he that is joined unto the Lord is one spirit.