Similes and metaphors are often confused with one another as they are both forms of comparison and are similar.

A simile means to be like something. When people are conveying a message to someone else they often use similes to help the other person understand what it is they are saying. For example, someone may ask you how your trip to the dentist was. You may respond that you feel like a beaten up punching bag. This is an example of a simile. 

A metaphor takes it a step further. Instead of saying something is like another, we say it is another. "An education is the passport to your future" is an example of a metaphor. You are not saying it is like a passport, but it is a passport.

Here are some more examples:

Examples of Simile:

• She swins like a fish.
• He's as hairy as a gorilla.
• Peter laughs like a hyena.
• Mr. John is as wise as an owl.

Examples of Metaphor:

• He was a tornado, blasting his way through the opposing team.
• He was a lion in the fight.
• The moon was a ghostly galleon tossed upon cloudy seas.

These two figures of speech are quite similar.  They both compare one thing to another as a way of describing the first thing.  But they are different because a simile does this directly while a metaphor does it indirectly.

A simile always has the word "like" or "as" in it.  So, for example, you can say that death came and took someone away "like a thief in the night."  That is a simile -- it is saying that death and a thief are similar and it does so directly by using the word "like."

A metaphor does not use the word "like."  An example of this is from Romeo and Juliet.  Romeo says "It is the east, and Juliet is the sun."  He is comparing her to the sun, but he is not saying she is like it -- she is saying she is the sun.

A simile and a metaphor are both literary devices used to compare one thing to another or to transfer the sense or aspect of one thing onto another. The major difference is the fact that a simile is a type of metaphor whereas not all metaphors are considered similes.

A simile explicitly refers to comparisons that use the words "like" or "as" to connect the two concepts. 

Ex. "That house is as big as a mansion" or "He's tall like a tree."

Once more, this can also be considered a metaphor—however every other type does not need to use like or as as part of the connection. 

Ex. "Don't cross that bridge before you come to it" is a metaphor for "don't worry about something before you need to."

A simile is a comparison that uses "like" or "as." 

"Sally was as red as an apple."

A metaphor is a comparison as well but it doesn't use "like" or "as," and the comparison is more direct.

For example: "Education is a vital instrument of progression in society." Education is being likened to an instrument very directly.