Starting with Christ’s priesthood, Christ is the unique mediator between the Father and the people. He effects that mediation both by interceding for the Church, representing the Church to the Father as head of the body of the Church, and as God's representative to his people, the Church, as the Bridegroom who betrothes the Church. The sexual imagery of Christ's mediation would lose its force if sex were merely contingent.
Ordained priests, in an analogous and derivative way, make real the dual role of Christ the Head. In baptism, we have all put on Christ; he has incorporated us into his body and each person acts in persona Christi. But to use the formulations of canon law, the priest is said to be acting in persona Christi capitis, of having the unique role of representing the 'headship' of Christ Jesus. The uniqueness of the priesthood is that Christ wills that his role as head and his pastoral presence be no less present than it was two millennia ago.
Christ the High Priest's two roles — representative and bridegroom — are fundamentally male, for whatever reason in the mystery of God. Theologically, the importance of the iconic meaning of Christ as male is paramount. On a purely physical level, the priest is the icon of Jesus, who was a man; but on a deeper level, the priest is the icon of Christ who comes as the Bride of the Church to conceive within the Church the life of grace, an icon for the whole mystery of Christ’s mediation of God to the people.