A metaphor is a comparison that does not use the words like or as. The Great Gatsby, an extraordinarily lyrical novel, offers a great wealth of metaphors A few examples are below.

In a famous metaphor from the novel, Gatsby likens the sound of Daisy's voice to money:

"Her voice is full of money," he said suddenly.

Nick extends the metaphor:

That was it. I'd never understood before. It was full of money—that was the inexhaustible charm that rose and fell in it, the jingle of it, the cymbals' song of it.

The man with the owl-eyed glasses compares Gatsby to the books in his library:

a triumph. What thoroughness! What realism! Knew when to stop too—didn't cut the pages.

Owl Eyes believes Gatsby is a fraud but that, like his books, he is not a cheap, cardboard imitation, but one that almost passes for what he pretends to be: one who has taken the time and the effort to seem real.

There are many metaphors associated with movement in the book, especially applied to restless women. Daisy and Jordan are described as if they are on a journey. This becomes an extended metaphor that is worth quoting at length:

The only completely stationary object in the room was an enormous couch on which two young women were buoyed up as though upon an anchored balloon. They were both in white and their dresses were rippling and fluttering as if they had just been blown back in after a short flight around the house. I must have stood for a few moments listening to the whip and snap of the curtains and the groan of a picture on the wall.

Likewise, the "confident" young woman at the first party that Nick attends at Gatsby's are compared to a sea:

glide on through the sea-change of faces and voices and color under the constantly changing light.

At the party that Tom and Daisy attend at Gatsby's, Gatsby points out a movie star whom Nick likens to an orchid:

Gatsby indicated a gorgeous, scarcely human orchid of a woman.

F. Scott Fitzgerald's The Great Gatsby has some of the richest language in all of American literature. He wrote the novel at a time when rich language was frowned upon by the most popular writer of that era, Ernest Hemingway. Some critics have even argued that Gatsby's language is what sets it apart in the American literary canon, not the actual story. 

To answer this question, I'm going to look at the general idea of metaphors (all analogies—similes, personification, extended metaphor).

Fitzgerald uses figurative language extensively to stimulate the readers' senses (imagery) and to create tone. Some examples of Fitzgerald's figurative language include his description of Gatsby's party guests who "came and went like moths among the whisperings and the champagne and the stars." In addition, when Nick and Mr. McKee "groaned down" in an elevator, he loads the phrase with innuendo. At Gatsby's party, no one carries the cocktails; instead it "floated at us through the twilight."

To me, one of the greatest metaphors in all of American literature is the novel's last paragraph:

"So we beat on, boats against the current, borne back ceaselessly into the past." 

In this metaphor, the narrator directly compares the human drive to achieve a dream to "boats against the current." This image is a particularly strong one in that it helps the reader visualize the difficulty one may face.

It's always important to recognize metaphor, but it's more important to understand why the author makes these choices.

As a lyrical Romanticist, F. Scott Fitzgerald made much use of the beauty of metaphor which makes language transcend the mundane into the limitless realm of imagination; certainly, metaphor is appropriate to his character of Jay Gatsby who has re-invented himself as a romantic hero come to retrieve the young excitement of his evenings with Daisy, who, like the Sirens, has enchanted him.

It is important to note that metaphors may take one of four forms, depending upon whether the literal and figurative terms are respectively actually named, or are simply implied:

1. literal and figurative terms are both named
2. literal term is named, but figurative term is implied
3. literal term is not implied and figurative term is named
4. literal term is implied, and the figurative term is implied as well. 

(Sometimes students do not recognize metaphors when they are implied.)

Here, then, are examples of metaphors used in The Great Gatsby:

• In Chapter Three Nick sees a car stuck in the ditch by the road; "a pale dangling individual stepped out of the wreck."
• In Chapter Four Fitzgerald describes Gatsby's car that is resplendent with all its boxes to hold hats and picnic lunches, and so forth.

...terraced with a labyrinth of windshields that mirrored a dozen suns. Sitting down behind many layers of glass in a sort of green leather conservatory... 

Windshields are compared to a labyrinth; the light reflected off the car (implied) is compared to "a dozen suns"; the interior of the car (implied) is compared to a conservatory.

A metaphor describes something through the use of images or descriptions that are not literally what is being described. Metaphors make comparisons between the actual object of the description and the phrase or image to which it is being compared.

During one of the parties at Gatsby's house, Nick observes the moon rising over the bay. He describes it as "floating in the Sound...a triangle of silver scales, trembling a little to the stiff, tinny drip of the banjoes on the lawn."

After another party, Nick begins to become more aware of unavoidable rumors and gossip about Gatsby's background. Nick still fundamentally doesn't believe the tales he has heard, but can't ignore the intrusion of the rumors any longer. His way of picturing the outside forces intent on destroying Gatsby's reputation:

On Sunday morning while church bells rang in the villages alongshore, the world and its mistress returned to Gatsby's house and twinkled hilariously on his lawn.

On another occasion, Gatsby points out a delicately beautiful woman to Daisy and Tom. "'Perhaps you know that lady,' Gatsby indicated a gorgeous, scarcely human orchid of a woman..."