According to McConkie and Millet, all gospel ordinances are teaching devices, all testify of Christ and of our need to be one with him. Alma’s illustration of this verity is the priesthood. The manner in which a man was called, ordained, and served in God’s name typified the call, ordination, and service of God’s own Son.
In Alma 13:17-19 Alma establishes Melchizedek as a type for Christ, noting the following parallels:
1. Like Christ, Melchizedek was a king. The very name of this great high priest--Melchi-zedek, “king of righteousness” or, perhaps more correctly, “my king is righteousness”--affirms and testifies of the goodness and the power of the coming Messiah. Righteousness is also a name-title of Christ (see Moses 7:45). As Melchizedek ruled his kingdom in righteousness, so Christ will eventually rule and reign upon this earth, doing so with the unchanging scepter of righteousness and truth, possessing an everlasting dominion without compulsory means (see D&C 121:46).
2. Melchizedek ruled over the city of Salem (a name which means “peace”). In like manner, Christ will reinstitute the glory of David‘s day when nought is known but peace among the Lord’s people.
3. Both Melchizedek and Christ were known as the “great high priest.” In Old Testament times the primary duty of the priest was to offer sacrifice at the altar and to act as mediator between God and men. It was by virtue of the priestly functions that the nations of Israel were reconciled to their God. “Through the ministrations of the priesthood the people of Israel were instructed in the doctrine of sin and its expiation, in forgiveness and worship. In short, the priest was the indispensable source of religious knowledge for the people, and the channel through which spiritual life was communicated.” (International Standard Bible Encyclopedia 4:2439).
4. Both were men of “mighty faith” who taught “repentance” to their people. Of Melchizedek we read, “his people wrought righteousness, and obtained heaven” (JST, Genesis 14:34). And of course the same will be true of all who sustain Christ and his teachings in righteousness.
5. Both bore the title Prince of Peace, being teachers of that gospel by which peace and joy come.
6. Of Melchizedek we read, “and he did reign under his father,” as does Christ, who professes no authority save that of his Father (see John 5;30).
7. Though there were many prophets before Melchizedek and many after him, Alma described the king of Salem by saying “none were greater.” Thus this great prophet, priest, and king stood as a classic type of the Promised Messiah, of whom it is true not only that none were greater, but also that none have been as great. [Joseph F. McConkie and Robert L. Millet, Doctrinal Commentary on the Book of Mormon, Vol. III, pp. 102-103]