Singing is a universal feature of the human experience. People from all over the world sing for a variety of reasons. Have you ever found yourself singing or humming subconsciously when you're in a good mood?
Particularly for the Christian, we sing because of our joy in God. Singing comes naturally to us, because of what we know about Him. One thing that makes us want to sing is His love. We see an example of this is Psalm 13:5-6.
But I have trusted in your steadfast love; my heart shall rejoice in your salvation. I will sing to the LORD, because He has dealt bountifully with me. (Psalm 13:5-6)
After feeling abandoned by God in the beginning of the psalm, the psalmist now acknowledges God's steadfast love. He knows that God faithfully loves His people, and he now returns to trusting in that steadfast love. He anticipates being saved by God, and he knows that he will rejoice in that salvation.
He sees that God has already dealt bountifully with him, has already shown him abundant grace. And the result of all this is that the psalmist wants to sing. "I will sing to the LORD".
Singing is one of the most enjoyable aspects of Christian worship, because in it, we recall God's steadfast love, His salvation, His bountiful dealings with us. Beyond that, we relish God's character and attributes. We appeal to Him for help. And we do it in a way where we express all this in beautiful melody, as invented by the Creator Himself.
When we sing to God, it glorifies Him. And it blesses us!