Since biblical times the Church has been known as the bride of Christ (cf., Eph 5:21-35). This is an important metaphor for understanding what it means to be Christian. The two elements that create an unbreakable marriage covenant are consent and consummation – when the couple says “I do” with their words, and then with their bodies. It’s the difference between formal union and real union.
The covenant between Christ the Groom and His bride the Church is no different. The consent occurs at baptism, when, after “I do’s” are proclaimed the new member of the bride is washed of his or her old identity and is given a new name. The consummation that solidifies the union and renews the covenant when repeated is the Holy Eucharist, when “the two become one flesh.” In this intimate Communion of bride and Groom, the real Christ enters our bodies and fills us with His life, impregnating us with grace.
This distinction between consent and consummation is very important. It means Christian communities that have apostolic succession, i.e. Catholics and Eastern Orthodox, have a real marital-like relationship with Christ, united in both words and bodies. On the other hand, Protestant communities that broke from the mystical body and apostolic succession have baptism but n Eucharist; hence, they are ‘married’ in the legal sense to Christ the Groom but do not ‘live as husband and wife’.
One’s personal subjective faith, of course, makes a great difference in the divine-human relationship; but, objectively, we are ultimately talking here about the difference between ‘intimate marriage’ and ‘friendship marriage’.
When Jesus begged His Father that they may be one in Him as He is in the Father at the Mount of Olives (Jn 17), He may have had the Last Supper in mind, the first Eucharist just previously celebrated with His apostles. It is the will of the heavenly Groom that all members of His bride know the fullness of intimacy of the New Covenant relationship, not just the friendship part that depends solely on words.