When a judge enters a courtroom, the instruction is given for all to rise.  It is a way of showing honor.

King George II of England is said to have risen at the singing of the "Hallelujah Chorus."  It was the London premier of "The Messiah" in 1743.  The music, composed by George Handel, was moving, and so were the words.  And very applicable to a king.

King of kings and Lord of lords

And He shall reign forever and ever.

"King of kings."  The words continue with Revelation 11:15:

The kingdom of this world is become the kingdom of our Lord and of His Christ.

Jesus talked about the end of the age.  It will usher in the kingdom of God.

For the Lord God Omnipotent reigneth.

Over and over, "Hallelujah" is sung, which means "Praise the Lord."  The music is an expression of triumph.

The "Hallelujah Chorus" comes at the end of Part 2 of "The Messiah"--Part 3 is still to come.  The throne of God continues to be a theme with Part 3 ending with "Worthy is the Lamb."

Blessing and honor, glory, and pow'r

Be unto Him, that sitteth on the throne,

And unto the Lamb, forever and ever.

The oratorio concludes with many "Amens."