A metaphor is a figure of speech in which a word or phrase is applied to an object or action, to which it is not applicable.
In simple words, a metaphor is a figure of speech that makes an implicit, implied, or hidden comparison between two things that are unrelated, but which share some common characteristics
The classroom was a zoo
1. He is a night owl
Owls generally do not sleep at nightand therefore a person who is awake at nightis compared to an owl.
2. The storm was a raging bull
A raging bull is fast, dangerousand does not look around to see who is getting affected. A storm which is similar to the bullis compared here to give the effect that it was dangerous.
3. He is a shining star
A shining star, with its bright light stands apartfrom the rest of the group. A person who is outstanding and performs wellis a shining star.
4. Laughter is the music of soul
Music is always pleasant and gives hope. Therefore laughteris said to be the hope giver to the soul.
Metaphors are used to dramatize thoughts to emphasize and elevate the expression to a higher intensity. Unlike similes, it does not use any words "as" or "like" to bring about the comparison. It compares by saying  X is Y, rather than saying X is like Y or X is as Y as Z.
How to identify whether a statement is a simile or metaphor? Check for words "as" or "like" - if it is present, it is a simile. If not, it is a metaphor.
In the above example, the meaning to be conveyed is the sun is looking like a golden ball.
In simile terms, it will be "The sun is like a golden ball"
In metaphoric terms, it is "The sun is a golden ball"
Metaphors are interesting because it is indirect and keeps the reader guessing to find why the comparison was made. Literal meanings are ignored and metaphoric meanings are used to give depth and drama to the thoughts that are expressed.
Metaphor in the lesson:
It's the old home roof that shelters....
There you find the gladdest play-ground...