Revelation 1 describes Jesus with three titles: faithful witness, firstborn of the dead, ruler of the kings of the earth. 

Revelation 1 describes Jesus work with another triad: He loved us, loosed us from our sins, made us a kingdom of priests.

The two triads match: Jesus loves us as a faithful witness, giving Himself for us as witness to death; Jesus looses us from our sins by His resurrection as the firstborn of the dead; Jesus is ruler over the kings of the earth, the priest-kings He made in His death and resurrection.

That helps resolve an exegetical problem: Who are the kings over whom Jesus reigns? All rulers, or the community of kings that is the church? The structure indicates that, in this context, the latter is preferable (though of course Jesus is also King of all kings).