A metaphor means that two things are the same in all ways. For example, He is a pig means that he is like a pig in many ways: size, appetite, manners, etc.
A simile, however, means that the two things are the same in 1 way. For example, He is fat like a pig or He is as fat as a pig means that he is very fat.
|Structure||A is B||A is like B OR A is as _____ as B|
|Similarity between 2 things||All attributes||1 attribute|
"Metaphor vs Simile." Diffen.com. Diffen LLC, n.d. Web. 20 Aug 2014. < http://www.diffen.com/difference/Metaphor_vs_Simile >