I have a couple of observations when reading this passage: first, singing is a representation of God’s joy. Some Biblical translations word this verses as “he rejoices over you with a shout of joy.” He Rejoices. You have been His joy and you continue to be His joy.
Second, if you go on to read verse 14 you see that God’s singing parallels the singing of His people in Jerusalem. This whole passage of scripture begins with the people of Jerusalem singing praise to God and flows into God singing over His people. God rejoices with His people, and He also expresses joy when His people sing praises to Him.
But what is it about us that makes God so joyful? This passage of Zephaniah speaks of a future time. A time when God has ended His judgment upon Israel. All of their enemies have been destroyed, and Israel is entering a time of safety and blessing (verses 8, 15, 19). Zephaniah is speaking of the future millennial kingdom when the Messiah (Jesus) will reign with His people in Jerusalem (Isaiah 9:7; Revelation 20:1–6).
The picture painted in Zephaniah 3:17 is emotion filled. Just like a loving parent gently rocks a child to sleep while sings out of love, so God’s song over His people is birthed from His great love. As we face the hardships of life, our loving Father is there to dry the tears of His people’s, comfort their hearts, and draw them closer to Him.
Also, Jesus teaches in Luke 15 that “there is joy before the angels of God over one sinner who repents”. It is not clear if God Himself is singing, but it is clear that there is rejoicing in God’s presences, over each one that was lost and has now repented.