A major analogy is that of the body. Just as husband and wife are to be "one flesh", this analogy for the writer describes the relationship of Christ and . Husbands were exhorted to love their wives "just as Christ loved the " and gave himself for it.
The analogy used here is that of a body, just as husbands and wives are one flesh, so too should the writer's relationship with God be described.  Husbands were told to love their wives in the same way Christ loved the Church and gave his life for her.