Learn more about Melchizedek from the Easton’s Bible Dictionary

King of righteousness, the king of Salem (q.v.). All we know of him is recorded in Gen. 14:18-20. He is subsequently mentioned only once in the Old Testament, in Ps. 110:4. The typical significance of his history is set forth in detail in the Epistle to the Hebrews, ch. 7. The apostle there points out the superiority of his priesthood to that of Aaron in these several respects, (1) Even Abraham paid him tithes; (2) he blessed Abraham; (3) he is the type of a Priest who lives for ever; (4) Levi, yet unborn, paid him tithes in the person of Abraham; (5) the permanence of his priesthood in Christ implied the abrogation of the Levitical system; (6) he was made priest not without an oath; and (7) his priesthood can neither be transmitted nor interrupted by death: "this man, because he continueth ever, hath an unchangeable priesthood."
The question as to who this mysterious personage was has given rise to a great deal of modern speculation. It is an old tradition among the Jews that he was Shem, the son of Noah, who may have survived to this time. Melchizedek was a Canaanitish prince, a worshipper of the true God, and in his peculiar history and character an instructive type of our Lord, the great High Priest (Heb. 5:6, 7; 6:20). One of the Amarna tablets is from Ebed-Tob, king of Jerusalem, the successor of Melchizedek, in which he claims the very attributes and dignity given to Melchizedek in the Epistle to the Hebrews.