Set a timer for 5 to 10 minutes and write as many metaphors or similes as possible for one concept (eg first love, confusion, or determination). Try not to lift your pen off the page for too long, or if you’re writing on a computer, keep steadily typing. Don’t question the relevance of any one metaphor while doing this, just write whatever metaphors come to your head, as you can always edit them later.
After you’ve done this exercise, either select your favorite metaphor and expand on it, or try writing a poem including many metaphors for the same concept, approaching the subject from many angles. How does each metaphor build toward the reader having a visceral understanding of the concept?
For an example of a poem that contains a lot of similes/metaphors for one concept, read: Tim Seibles’ First Kiss.