Psalm 3 is a psalm of disorientation stage two and more specifically a Psalm of Trust. It is written in a time of danger for David and he expresses that God has protected him so far and will continue to till He delivers David from his enemies.
The elements that confirm this observation are the portrayal of the distress (3:1, 2) and the declaration of confidence (3:3, 7-8). Also, there is no questioning of God or attacking of God as there is in a psalm disorientation of stage one, confirming that this psalm is a psalm of disorientation stage two.
The Psalmist uses many different imagery techniques in this psalm. First in 3:3a, the Psalmist uses a metaphor by calling Yahweh a shield that protects him, which is a frequent metaphor used psalms where the person is in danger of being attacked (cf. Psalm 7:10; 18:2, 30, 35; 28:7). The shield is a defensive item used when being attacked by adversaries, so Yahweh is the one who protects the Psalmist from his adversaries' attacks.
Following that in 3:3b, the Psalmist goes on to use a metonymy where he portrays Yahweh as lifting up his head. The lifting of the head represents the emotional change from helplessness and despair leading to depression into confidence and hope. He would undoubtedly by saddened by the persecution of his enemies. However, in trusting in the promise of Yahweh to protect him, his demeanor drastically.
In 3:6 the multiple enemies that were continuously attacking him made the Psalmist feel like there was was no way of escape (without trusting in the Lord). Therefore, the author represents his persecutors as having surrounded him with a great number of people. However, the author no longer feels this emotional truth the hyperbole portrays as the Psalmist states he has no fear of his enemies who attack as if they surround him.
In 3:7a the Psalmist personifies Yahweh as rising, or to be more specific it is an anthropomorphism of God. The Psalmist uses the same Hebrew word there for rise (qumah) as in 3:1 (qamim). So, the psalmist speaks of Yahweh doing the same thing that his adversaries were doing in order to represent Yahweh countering the adversaries because just as the enemies were rising up against the Psalmist in order that there would be no deliverance from God (3:1-2), so God will rise up and save him (3:7ab). After speaking of Yahweh's response in 3:7ab, the Psalmist goes on to discuss the fate that Yahweh will bring upon their enemies by striking their cheek and breaking their teeth. These are metonymies that describe the physical action that happens in battle to represent their defeat (if not death).
Finally, in 3:8b the author speaks of (or requests) God's blessings to be upon His people, with the blessing of salvation being implied. Here, the author uses the people as a whole (perhaps to represent Yahweh's faithfulness promised earlier in the Old Testament) to apply to himself as a indiviudal who is in need of salvation from his enemies (synechdoche). By applying the promise of the whole to himself, he portrays an image of certainty and trust of deliverance from his enemies by Yahweh.
In Psalm 3, the primary structure the author uses are couplets, but the author also uses one tricolon and maybe one or two quatrains.
The second line intensifies the first line, where there are many enemies and they are then spoken of as attacking the Psalmist. Furthermore, in the final line of 3:2 the Psalmist portrays the state his enemies perceive the Psalmist to be in, further intensifying the first two lines by implying the Psalmist was in a grace situation. The conflict that is to be solved is immediately presented and so it sets the tone for the rest of the psalm.
3:3 Couplet (maybe a Quatrain with 3:4)
The lines in this couplet complement each other. Whereas the first line speaks of the protection that Yahweh will offer, the second line speaks of the renewed confidence the Psalmist has. One might go on to say that the second line is subordinate to the first line by saying that as a result of the protection from Yahweh, the Psalmist has a renewed confidence and hope. This couplet gives the answer to the conflict 3:1 presented and shows the trust Psalmist has in Yahweh.
3:4 Couplet (maybe a Quatrain with 3:3)
The Psalmist here is perhaps explaining the reason for his trust in Yahweh in 3:3 (so one might could say 3:3-4 is actually one quatrain instead of two couplets). The answer in the second line is a continuation of the cry to Yahweh in the first line. The Psalmist is portraying the goodness and faithfulness of Yahweh in answering his cry. In addition, by the cry and response being in immediate succession the Psalmist might also be implying that Yahweh answered immediately without delay.
In this two lines, the Psalmist speaks of going to sleep in a time of persecution. The normal psychological response to being attacked is to avoid sleep as much as possibility as it becomes a time of vulnerability to be attacked. However, the second line is a continuation in saying that he woke up, which is ascribed to Yahweh. This continuation gives the idea of safety even in the most vulnerable times.
3:7ab Couplet (maybe a Quatrain with 3:7cd)
In these two lines, the Psalmist makes two requests of Yahweh which the second request being a continuation of the first. First, Yahweh is asked to rise, which is to follow to do the same action which the Psalmist's adversaries had taken (3:1). Then Yahweh is asked to saved him, which is to oppose the action of his adversaries who were attacking him and said there was no salvation/deliverance for the Psalmist. The continuation of the second line from the first taken portrays an equal response to how the adversaries are portrayed in this psalm.
3:7cd Couplet (maybe a Quatrain with 3:7ab)
These two lines may be considered subordinate to 3:7ab and so 3:7 as a whole might be considered one quatrain instead of two couplets. Regardless, the author expresses confidence in Yahweh to attack his enemies in response. The second lines is essentially a restatement of the first which goes on emphasize the response of Yahweh to the Psalmist's enemies and the certainty of Yahweh's response. Also, in the first line the enemies are the Psalmist's, whereas in the second line the Psalmist speaks of the wicked which implies being against God. In equating the two lines, the Psalmist might also be speaking his adversaries being also enemies of God, which would show a greater sense of certainty that God will respond.
The second line here is a intensification of the first line, which goes to show the certainty the Psalmist has in Yahweh and His faithfulness. The first line speaks of the salvation belonging to Yahweh, which means that Yahweh has the ability to save. However, ability without being used would mean nothing for the Psalmist and wouldn't mean that Yahweh is faithful, so in the second line the Psalmist speaks of Yahweh blessing His people (implying bestowing salvation to His people, of which the Psalmist was one). So the second line shows that God is not only able, but willing to save. An alternate interpretation might be that the second line is a request of the Psalmist to Yahweh to ask for God to bless His people. Regardless, there is a sense of trust in God that is portrayed by the second line.
The psalm starts off with the distress the Psalmist faces from his adversaries (3:1-2). However, the Psalmist immediately goes to speak of God's protection of him with the result of the Psalmist having a renewed confidence and hope (3:3). This confidence is placed in the fact that he cried out to Yahweh and Yahweh responded (3:4). So the Psalmist has enough confidence to sleep, when he would be vulnerable, and then wake up because of Yahweh's protection (3:5), therefore he does not fear the many people are who attacking him constantly as if they surround him (3:6). Then he goes on to ask for Yahweh to rise and save him by attacking their mutual enemies (3:7). Finally, the psalm is summed up with the ability to save being the ability of Yahweh and having confidence (either by statement or request) that Yahweh will bless the Psalmist with bless him with deliverance from his enemies.
Also, the end of the poem gives the final response or solution to the problem or distress given in the beginning of the poem, so the author progresses from distress to confidence. Intermittently, the author synthesizes statements of confidence of safety and then requests to God for deliver, as if he is presently praying while trusting Yahweh to respond.
Psalm 3 is one of many psalms in the psalter that express confidence in God to deliver people from those who persecute them. These psalms remind people that when one is being attacked by others, either physically or in other manners, that they should turn to God and trust that He will deliver them from the attacks of their enemies.