The word 'metaphor' is used frequently to describe the comparison between things, but we need to be careful as writers and editors that we are actually using the term 'metaphor' correctly. For example:
The man laughed like a child being tickled by his father.
Nice metaphor, right? Wrong! The above example is not a metaphor, it is a simile.
A simile is "[a] figure of speech in which two essentially unlike things are compared, often in a phrase introduced by like or as." Source
Whereas a metaphor is "[a] figure of speech in which a word or phrase that ordinarily designates one thing is used to designate another, thus making an implicit comparison, as in "a sea of troubles" Source
Therefore, whenever you compare things with a 'like' or 'as' it is a simile. Whenever you directly compare things without the like or as, it is usually a metaphor.
Do you have any examples of metaphors or similes you would like to share?