Enter his gates with thanksgiving,
and his courts with praise!
Give thanks to him; bless his name!
With just five short verses, Psalm 100 gets a whole lot of praises sung to God. It calls the entire planet to worship the Lord in the first verse, appealing for a global choir to make some seriously joyful noise. The psalm equates glad service with praise in the second verse, confirming that doing service for God is a way to acknowledge the praise that is due to God.
The third verse reminds us of the basic reason for our praise -- God is our Creator and we belong to Him. He loves us and leads us like a shepherd cares for His flock. That leads us to expressions of thanksgiving in the fourth verse. We are encouraged to be thankful even as we enter into the places in which we worship Him.
The fifth verse ends the song giving us a second reason why we should do this: because God is good to us, loving us forever and is faithful across generations. God will never fail us, so our praises should never stop flowing from our grateful hearts to Him!