1. Melchizedek and Levi

2.  From Dictionary.com  Noun, Origin of priest, Middle English -prest, Old English – prēost, Late Latin - presbyter  1. a person whose office it is to perform religious rites, and especially to make sacrificial offerings.  2. a person ordained to the sacerdotal or pastoral office; a member of the clergy; minister. (in hierarchical churches) a member of the clergy of the order next below that of bishop, authorized to carry out the Christian ministry.  3. a minister of any religion.  4. to ordain as a priest. (verb (used with object)

3.  Genesis 14:18-20  Melchizedek, king of Salem,* brought out bread and wine. He was a priest of God Most High. He blessed Abram with these words: “Blessed be Abram by God Most High, the creator of heaven and earth; And blessed be God Most High, who delivered your foes into your hand.”Then Abram gave him a tenth of everything.

5.  A priest is one who offers sacrifice, and Melchizadeck offered “bread” and “wine” and he was the king of Salem, ancient Jerusalem. He pre-dates the Levitical priesthood from Aaron’s line by about 3-400 years.  Some commentators suggest that the Biblical Narrative suggests that Melchizadeck may be the character Shem, the son of Noah from the pre-historical accounts in the first 11 chapters of Genesis.

6.  There is an excellent article on the Priesthood from http://newadvent.org/cathen/12409a.htmhttp://newadvent.org/cathen/12409a.htm  In one sense there is only one priest and that is Jesus Christ who is priest, prophet and king.  All baptized Christians participate in a very real way in this priesthood.  Henri de Lubac wrote a great book, The Splendor of the Church, an I think he makes a very good distinction between the priesthood of the baptized and the ministerial priesthood. All the baptized reveal this reality internally, while the ordained reveal it in a more external way.

7.  There are Bishops (episkopos), priests (presbyteros), and deacons (diakonos) in the New Testament. The elders (episkopos and presbyteros) role to bind and loose: Matthew 16:19; 18:18, and John 20:19  Also Jesus sets the apostles apart to forgive sins in the upper room, see John 20:19  One can see the development of this organizational structure in the pastoral epistles.

8.  To Preach: The priest is tasked with sharing the kerygma, the central message of Christ’s salvation  To Sanctify: the presbyter’s role is to administer the sacraments, especially the Sacrifice of the Mass and Reconciliation.  To Govern: The presbyter assists the bishop in the care and administration of the church at the local level, the respective parishes.