A metaphor is an implied comparison using neither 'like' nor 'as'.
These are some examples of metaphors: The tree was a tower, and the lawn was fields of wild grasses. The children running across the yard were knights mounted on wild, black stallions.
allegory
epic simile
The term is "simile" - a direct comparison of a specific attribute or set of attributes.
Simile
A comparison without using a connection word is called a metaphor. The connection word is like or as.
allegory
A comparison using like or as is a simile. A comparison without them is a metaphor.
An implied metaphor is a metaphor that makes a comparison without directly stating the comparison. An example of an implied metaphor is saying someone squawked out a reply, because it implies that they are talking like a parrot without saying it outright.
An epic simile. There are numerous examples in Homer's The Odyssey. What qualifies a simile is the comparison of two things (ie. "his heart was like a lion's") using the words "like" or "as". To qualify as an epic simile the comparison is extended using inflated language and poetic description.
Simile.
It is a simile, because it is a comparison using as, and a simile is any comparison using like or as.
A sentence using "like" or "as" to compare two things is called a simile.