“The LORD hath sworn, and will not repent, Thou art a priest for ever after the order of Melchizedek.” (Psalm 110:4)
The importance of this verse is indicated both by the fact that it is a Psalm, which is quoted at least 12 times in the New Testament. This verse is also central to the main theme of chapters 5–7 of Hebrews. It is quoted no fewer than five times in the book Hebrews. Melchizedek (or Melchisedec) himself is mentioned nine times. It refers to the strange appearance in Genesis 14:18-20. The Lord makes the point that when Melchizedek’s name is translated, he is the “King of Righteousness.” When the remainder of his description, the “King of Salem,” is translated, he is also the King of “Peace.” Some claim that Salem was a former name of Jerusalem, but there is no evidence to make such an assumption. Such hardly does justice to the exalted descriptions of Melchizedek in Scripture. He is the “priest of the most high God” (Heb. 7:1), suddenly appearing, and then disappearing as mysteriously as he came.

The Lord makes the point that Melchizedek is greater than Abraham (Heb. 7:4), and greater than Aaron, the founder of the Levitical priesthood. Furthermore, he was “without father, without mother, . . . having neither beginning of days, nor end of life; but made like unto the Son of God; abideth a priest continually” (Heb. 7:3). Such a description is not consistent with the claim that his genealogy is just not recorded.

Some have postulated that this Melchizedek was a pre-incarnation of Christ. If that be true, they must explain why the Scriptures make a great point of the Father’s declaring with an oath that Jesus would be after the order of Melchizedek. Why swear with an oath if Melchizedek were Christ himself. He would not need to swear but merely declare that Christ is Melchizedek. Secondly, they must explain the present tense language that Melchizedek is made like unto the son of God who abides a priest continually (Heb. 7:3).

The only point one can take of such a description is that, because Christ was made a priest after the order of Melchizedek, that proves that his priesthood is eternal. I can see no other point made in these verses concerning Christ. Can we assume that throughout eternity there has never been any being besides men or angels? Consider that eternity is a long time, and to think that God has done nothing forever and ever before he created the earth may be assuming too much.

For a deeper study of Melchezedek go here.

For further study of the spiritual realm, please see these PPT lessons online:
Spiritual Sight—Lesson 1
Spiritual Sight—Lesson 2