And hast made us unto our God kings and priests: and we shall reign on the earth. -Revelation 5:10

The most honorable of all monarchs to have ever been esteemed are those who had a right not only to royalty, but to sacerdotal supremacy-those kings who could wear at one time the crown of loyalty, and at another the mitre of the priesthood, who could both use the censer and hold the sceptre-who could offer intercession for the people, and then govern the nations. Those who are kings and priests are great indeed; and here you behold the saint honored, not with one title, or one office, but with two. He is made not a king merely, but a king and a priest; not a priest merely, but a priest and a king. The saint has two offices conferred upon him at once, he is made a priestly monarch, and a regal priest.

They are kings. They are not merely to be kings in heaven, but they are also kings on earth; for if my text does not say so, the Bible declares it in another passage: “Ye are a chosen generation, a royal priesthood.” We are kings even now… Every saint of the living God, not merely has the prospect of being a king in heaven, but positively, in the sight of God, he is a king now; and he must say, with regard to his brethren and himself, “And He hast made us,” even now, “unto our God kings and priests; and we shall reign upon the earth.” A Christian is a king. He is not simply like a king, but he is a king, actually and truly. ~ C.H. Spurgeon

http://www.blueletterbible.org/Comm/spurgeon_charles/sermons/0010.cfm