This is one of my favourite poetry exercises and I've used it with adults and schoolchildren. You write about people/relationships by comparing them to various things to create extended metaphors.
1. Think of a person/relationship you would like to write about.
2. Ask yourself the question: If this person were an animal/piece of clothing/piece of technology/building, what kind would they be? Why? What are the similarities? Make some notes.
3. Now form your main ideas into a short poem.
Here are some of my own efforts.
Why not have a go yourself and post one as a comment?