Psalm 36 is yet another appeal to God for His judgment upon the wicked in conjunction with deliverance for the righteous.
The face of evil is described in vs. 1-4. The wicked are said to be corrupt to the core, have no fear of God, and flatter themselves that they are safe from discovery. Their minds and mouths are full of plotting.
Our attention is turned to God in vs. 5-9. The psalmist sings of God's great love, His unfathomable justice, and His generous providence. (I especially love the poetry of vs. 9: "For with you is the fountain of life; in your light we see light.")
Finally, the psalmist and his righteous peers are brought in for consideration at the end of the psalm, vs. 10-12. In contrast to the wicked, David pleads for God's continued love and salvation. The righteous will be rescued from the "foot" and "hand" of the evildoers, who will be be unable to rise.