An extended metaphor is a comparison that is developed at length, perhaps over several line of writing or even an entire work, such as a poem. I'm Psalm 23, how does the speaker extend the metaphor that compares God to a shepherd? What feeling does this metaphor evoke?

Psalm 23 develops an extended metaphor on the relationship that God has with humans, by comparing it to the relationship that a Shepherd and his sheep have.

Answer

The author establishes the metaphor from the very beginning of the Psalm:

"The Lord is my shepherd, I lack nothing" (Psalm 23:1)

Then, he further develops this metaphor by enumarating the different tasks that a Shepherd carries out in order to take care of his sheep:

"He makes me lie down in green pastures" (vs 2)
"He leads me beside quiet waters" (vs 2)
"He refreshes my soul" (vs 3)
"He guides me along the right paths for his name's sake" (vs 3)
"I will fear no evil for you are with me; your rod and your staff they comfort me" (vs 4)

All these actions consist of specific things that only a shepherd would do with his sheep. Sheeps are considered to be animals with a limited eye view, this makes them clumsy and an easy target. David is comforted to know that God looks after him, since human beings are also weak and they don't always know what is best for them. This metaphor, therefore, evokes a feeling of caring, love and compassion towards human beings. Sheeps,then , are in a position of creatures and they can't return the shepherd the love and the care that is given to them. This makes the love that is given by the shelpherd a selfless love.