God’s people are described as both a “called out” people and “kings and priests” who shall reign on earth. We have the description of both the church and kingdom.
The royal priesthood would be meaningless without the High Priest. Christ became our high priest to offer his own blood for our sins (Heb. 8:4). He is a priest after the order of Melchisedec (Heb. 6:20; 7:17; 3:1). Melchizedec was king of Salem and priest of the most high God at the same time (Heb. 7:1). He had none who preceded him and none who would follow him in his priesthood. Christ was a priest after this order. He was of the tribe of Judah, of which tribe Moses said nothing concerning priesthood (Heb. 7:15). His priesthood will be forever after the order of Melchisedec (Heb. 7:17). We have such an high priest now in the heavens, and he is Jesus Christ (Heb.4:14).
Christ became high priest after he ascended into heaven, because he could not be a priest on earth (Heb. 8:4). But when he ascended into heaven to the right hand of God, he received dominion, and glory, and a kingdom (Psalm 110:1-4; Dan. 7:13-14). When Christ sat down on the right hand of God and began to rule as king, and he would be a priest on his throne as he reigned. “Even he shall build the temple of the Lord” (the church-HEP) “and he shall bear the glory, and shall sit and rule upon his throne; and he shall be a priest upon his throne: and the counsel of peace shall be between them both” (Zech. 6:13).