First you should know the difference between similes and metaphors. "She eats like a bird" and "as cute as a button" are similes because they compare using the words "like" and "as." Metaphors are comparisons without using "like" and "as" and the concepts that are compared are often unalike. "My boss is a beast" is an example of a metaphor. An extended metaphor extends the metaphor mentioned in the first line throughout an entire poem or paragraph of prose. If you are writing your first extended metaphor poem, start off by creating a free verse poem. Then, you can move on to a structured style, such as a rhyming quatrain or rondel.
Read some examples of extended metaphor poems and notice how each successive line describes the comparison that is stated in the first line of the poem.
Draw a four-column table on a piece of paper with the following headings: people, animals, abstract nouns and concrete objects.
Write down at least five words under each column. For example, under "people" you could write "Samantha," "villain," "movie star," "stranger" or "mother." Under "animals" you could write "cat," "beast," "unicorn" or "hyena." Under "abstract nouns" you could write "life," "love," "jealousy," "beauty," "skill" or "memory." Under "concrete objects" you could write "storm," "filing cabinet," "sign," "jewel" or "factory."
Select two words from your table that you are creatively inspired to compare and thus form a metaphor with. You can either choose two words under the same heading or pick words from two different headings to create a comparison between two concepts that are even more unalike.
Write a first sentence to form the metaphor. For example, if you chose "life" and "filing cabinet," you could write a metaphorical sentence such as "My life is a filing cabinet."
Brainstorm, on a scrap piece of paper, phrases that are related to your metaphorical statement. Allow yourself to free-write for five to 10 minutes without judgment. Any word, phrase or sentence can be written down. Some phrases for "My life is a filing cabinet," might be "many files," "from birth to present," "memories by year," "first walk" or "the day I learned to swim."
Start writing a free verse poem where the first line is your metaphorical sentence and each additional line incorporates your favorite words, phrases or sentences from your brainstorming session. A free verse poem does not have to rhyme and the lines do not have to be the same length.
Avoid writing a paragraph structure; start a new line every time you think there should be a pause when someone were to read your poem out loud. This means that periods do not have to be inserted at the end of each line.
Read your finished poem out loud and edit the structure so that it naturally flows from line to line.