Nature and Animals
In the first half of the psalm, the speaker introduces an extended metaphor, comparing God to a shepherd and his followers to a flock. This use of natural imagery is continued, including the "green pastures" and "still waters." Overall, this associates religious faith with nature and the natural order, as well as associating it with an image of peace and serenity.
The Home
In the second half of the psalm, the speaker moves to a more human setting. The speaker describes how God "preparest a table before me in the presence of mine enemies... my cup runneth over," and how he will "dwell in the house of the Lord for ever." This imagery associated with home and comfort emphasizes how God provides the speaker with a feeling of security and protection.
Safety vs. Danger
The imagery of safety and danger are contrasted in this Psalm. Essentially, the speaker associates a life of faith with a calm and secure life, and reminds us of the dangers and threats that life might throw at us. The latter is described using dark imagery, such as the "valley of the shadow of death." Here, the speaker emphasizes that God protects him from the fears and evils of the world.
