Psalm 100 also forms a chiastic structure!
1A: Psa 100:1, Make a joyful shout to the LORD all the earth;
1B: Psa 100:2a, Serve the LORD with gladness;
1C: Psa 100:2b, Come before His presence with singing;
CENTRAL AXIS: Psa 100:3, “Know that the LORD, He is God; It is He who has made us, and not we ourselves; We are His people and the sheep of His pasture;”
2C: Psa 100:4a, Enter into His gates with thanksgiving;
2B: Psa 100:4b, Be thankful to Him and bless His name;
2A: Psa 100:5, For the LORD is good + His mercy and truth is everlasting.
It is obvious how the C pairs, are paired: come before His presence and enter His gates with singing and with thanksgiving! The B pairs are paired, in that we are glad in Him and thankful in Him for the same reason; and out of that gladness and thanksgiving, comes our service to Him by which we bless His name. The A pairs reveal the reason that all the earth has to shout joyfully before the LORD (and the reason that we come before Him with thanksgiving, that we serve Him with gladness, and that we bless His name): He is good, and His mercy and truth is everlasting!