Psalm 100 is a Psalm of thanksgiving that shows us 5 things:
1-Make a joyful shout to the Lord
2-Serve the Lord with gladness, come before His presence with singing
3-Know that the Lord is God and He made us. We are His people and the sheep of His pasture
4-Enter into His gate with thanksgiving and into His courts with praise
5-Be thankful to Him and bless his name