Psalm 18 can sound triumphalist and melodramatic. The use of metaphors from nature (images of thunderstorms and volcano eruptions comes to mind) to dramatize God's intervention seems like an indulgence in hyperbole.
But when seen in the light of David's desperation and depression in other passages, one can't help but share in his moment of ecstatic joy. If the preceding psalms (15-17) were immediate predecessors of this one, in real, historical time, then it is a moment of triumph to truly savor. David's agonizing patience has paid off. His tongue-biting trust and gritty refusal to succumb has been rewarded.