Poetry Terms: Extended Metaphor

Definition Metaphor's Family. A comparison of two unlike things that had a continuous series in a stanza or a line, without using like or as.
Significance It may help the poem by more a live to people. Most poets don't use extended metaphor that much, so it may make it more unique.
Example 

The willow is like an etching,

Fine-lined against the sky.

The ginkgo is like a crude sketch,

Hardly worthy to be signed.

The willow’s music is like a soprano,

Delicate and thin.

The ginkgo’s tune is like a chorus

With everyone joining in.

~"Willow and Ginkgo" 

by Eve Merriam