Psalms 100 was intended to be a song of praise in the Old Testament worship. There is evidence that this psalm (among others) was part of New Testament worship, as well.* The psalm, in its entirety, is quoted here.
“Make a joyful noise to the Lord, all the lands! Serve the Lord with gladness! Come into his presence with singing. Know that the Lord is God! It is he that made us, and we are his; we are his people, and the sheep of his pasture. Enter his gates with thanksgiving, and his courts with praise! Give thanks to him, bless his name! For the Lord is good; his steadfast love endures for ever, and his faithfulness to all generations” (Psalms 100:1-5, RSV).
One of the over-riding messages of Psalms 100 is that we sing to bring our hearts, our minds and our spirits into the presence of God. “Come before him with joyful songs” is another way of saying verse two. Our worship should be one of gladness. There is a joy that overwhelms us as we come into God’s presence. It excites us so much that we want to shout our thanks to the Lord. In our thanksgiving, we recognize that the Lord is good and his “steadfast love endures forever.”
As the psalm says, singing hymns of joy brings us into the presence of the Lord.