Extended Metaphor:
A metaphor developed at length, occurring frequently in or throughout a work.


Example:
Children are flowers.
Always growing
Bright, Cheery
Making people happy
They are all different.
Blooming at their own time when
they are ready to show
Eventually they will die.
They need nurturing to thrive.
Helpless
Waiting for approval.
By: Ali Ballweg


Explanation:
Ballweg makes her entire poem a metaphor to children and flowers. This adds to the significance  and helps the reader understand the comparison made. Also this metaphor adds to the constant cheerful flow of the poem, and doesn't change the rhythm. The purpose of making one extended metaphor of the comparison between children and flowers to show all the similarities between both of them, and not just one example, which can leave the reader hanging and not definite about the comparison.