Zechariah 6

Take the silver and gold, make an elaborate crown, and set it on the head of Joshua the son of Jehozadak, the high priest. v.11

Read chapter 6
Joshua was high priest at this time of the return from captivity.  He is personified as a type of Christ who is the Highest Priest.  Here Zechariah is to make an elaborate crown to put on Joshua.  This was unusual because priests were never crowned, only kings were.  Yet Zechariah is to place an elaborate crown of silver and gold on Joshua and tell of the One who is to come. This one is called the Branch for He will branch out and build the temple of the Lord and sit as both king and priest on the throne.  This is none other than Jesus Christ. Who is God in the flesh.  The only one who is both king and priest.
The temple was rebuilt after the captivity at this point in history, but the temple that is spoken of here is still future and will be built in the coming Kingdom, not by hands of man but by the Lord Jesus Christ Himself.  When Jesus came in his first coming we did not see him as king and priest, but we will soon as we wait for Him to return and take this place Zechariah portrays for us here.  This was not a sign that Joshua was to become king as well as priest but was for a memorial in the temple of the promised future.  It was a symbol for all to continue in God's work now for the blessings that will come later.
What does Jesus reigning as both priest and king mean to you?