I will open my mouth in a parable: I will utter dark sayings of old: In a parable - Or, I will give you instruction by numerous examples; see Psalms 49:1-4 (note), which bears a great similarity to this; and see the notes there. The term parable, in its various acceptations, has already been sufficiently explained; but משל mashal may here mean example, as opposed to תורה torah, law or precept, Psalms 49:1.
Related Commentaries of Psalms 78:2
Psalms 78:2
2 I will open my mouth in a parable: I will utter dark sayings of old: