…and from Jesus Christ, who is the faithful witness, the firstborn from the dead, and the ruler of the kings of the earth. To him who loves us and has freed us from our sins by his blood, and has made us to be a kingdom and priests to serve his God and Father—to him be glory and power for ever and ever! Amen. – Revelation 1:5-6 NIV
I can not state it better than this:
Sin leaves a stain of guilt and pollution upon the soul. Nothing can fetch out this stain but the blood of Christ, and Christ shed his own blood to satisfy Divine justice, and purchase pardon and purity for his people. Christ has made believers kings and priests to God and his Father. As such they overcome the world, mortify sin, govern their own spirits, resist Satan, prevail with God in prayer, and shall judge the world. He has made them priests, given them access to God, enabled them to offer spiritual and acceptable sacrifices, and for these favours, they are bound to ascribe to him dominion and glory for ever. [Matthew Henry Concise Commentary]