A metaphor is a phrase that we use to compare two things that are not alike but have something in common. For the most part, metaphors allow us to imagine what someone is trying to say by appealing to our senses. For example, someone might say that the marketplace was a zoo.
The marketplace isn't actually a zoo. But because of all the people walking around and chattering, you might see it like a zoo filled with all sorts of animals.
Here a few more common metaphors you might want to use:
"A heart of gold"
This refers to a person who is kind, good-natured, or generous. They use the term "gold" because it's something valued for its goodness.
"All the world's a stage"
This was first used by William Shakespeare in the play As You Like It. It means the world is like a stage where everyone is just acting to get through each day. It's cynical, but we can't deny the truth behind it.
"A diamond in the rough"
Saying that someone is a diamond in the rough is like saying that they are a good person who lacks manners, education, or style.
"A special snowflake"
If someone is described as a special snowflake, it means that person claims to have unique traits that entitle them to special treatment. For example, a special snowflake who claims to have a gluten allergy would demand that all their food be inspected for gluten.
To feel blue is to feel sad. Blue is often associated with sadness, which is why it's also found another common idiom - to have the blues.
Metaphors are a great way to convey how we feel without being too literal. That's why it's always a good idea to learn as many as you can!