The LORD is mentioned in vs. 1, 2, 3, 5.
The emphatic personal pronoun "He" is used twice in vs. 3 to emphasize the LORD.
Seven imperatives are used in the first four verses to direct us to the proper attitude and actions toward the LORD.

100:3 Know that the LORD He is God- Deut. 4:35 , 39; 7:9; I Kings 18:39 .
It is He who made us- He is our Creator and we are accountable to Him.
We are...sheep of His pasture- He provides for us and sheep- Ps. 23:1- and carries us- Ps. 28:9.

100:5 He is good, His lovingkindness is everlasting- I Chron. 16:34 ; II Chron. 5:13 ; 7:3; 20:21 ; Ezra 3:11 ; 106:1; 107:1; 118:1, 29; Jer. 33:11 .

Jesus and Psalm 100
Jesus is Creator- John 1:1-3
Jesus is Shepherd- John 10:1-18
The ultimate display of God's goodness, lovingkindness, and faithfulness is the cross!!!