"'Rock' is a common poetic figure for God (or the gods: Dt 32:31, 37; Isa 44:8), symbolizing his unfailing (see Isa 26:4) strength as a fortress refuge (see vv. 31, 46; 31:2-3; 42:9; 62:7; 71:3; 94:22; Isa 17:10) or as deliverer (see 19:14; 62:2; 78:35; 89:26; 95:1; Dt 32:15). It is a figure particularly appropriate for David's experience (see 1Sa 23:14, 25; 24:2, 22; 26:20), for the Lord was his true security." (The NIV Study Bible notes, Ps. 18:2)
