The role of metaphor is for the image/word to mean something other than what it is. Metaphors can change as they are applied to poems and they can change as the poet or reader see fit.
Poetry provides for alternative perspectives dependent on the time they were written. They are a reflection of society. For instance, Grace Nichols’ poem, “Tropical Death,” (http://nisababepraised.wordpress.com/2011/05/05/poem-of-the-week-tropical-death-plus-links/) plays up to the society she was raised in. It comments on how the speaker in the poem wants to be buried in her own country in the Caribbean where her roots originate rather than where she is in England.
As you read the poem, notice how the images play based on the words used to convey them. Witness the changes the metaphors go through as the poem progresses.
Further, a look at periodicals or advertisements claiming that there is the ‘death of the web,’ or the ‘death of literature’ or the ‘death of tax’ are examples of how death is used in the world.
Read W.S. Merwin’s poem, “For the Anniversary of My Death,” (http://www.poetryfoundation.org/poem/171868) and you will hear the voice of the speaker contemplating both his life and his death. He compares the two and concludes that death holds more meaning because it is infinite. Notice the changes the words go through.