In Genesis 14, there is a man named Melchizedek, but not very much is said about him:
17 After Abram returned from defeating Kedorlaomer and the kings allied with him, the king of Sodom came out to meet him in the Valley of Shaveh (that is, the King’s Valley). 18 Then Melchizedek king of Salem brought out bread and wine. He was priest of God Most High, 19 and he blessed Abram, saying, "Blessed be Abram by God Most High, Creator of heaven and earth. 20And praise be to God Most High, who delivered your enemies into your hand." Then Abram gave him a tenth of everything.
(Genesis 14:17-20, NIV)
He is also mentioned in one of the Psalms:
The Lord has sworn and will not change his mind: "You are a priest forever, in the order of Melchizedek."
(Psalm 110:4, NIV)
What is the importance of this character? This question has already been answered based on the New Testament book of Hebrews, but I'm looking for an answer based just on the Genesis text and the surrounding narrative or other contemporary sources.