Cup runneth over
In this poem, the phrase "cup runneth over" is used to emphasize how the speaker has everything he needs. However, this phrase is often interpreted as meaning a person has more than they need. Ironically, through history, this phrase has come to mean something different for many people.
The Host
Although God is a protector and "shepherd," he ironically treats the speaker as a welcomed guest. By depicting God as a host, the speaker acknowledges that God is not a tyrannical leader and is prepared to lower his status and serve others.
The valley of the shadow of death
Ironically, although the speaker walks through a very frightening place (the valley of the shadow of death," he does not have any fears. This is ironic as we might expect him to be fearful.
Sheep metaphor
God is depicted as being a shepherd in this psalm, while his followers are sheep. Although to contemporary readers this may have seemed like a positive metaphor, suggesting that his followers are looked after, to modern readers it might not seem so positive. This is because comparing followers to sheep suggests a lack of independence and agency.