Metaphor

What then is truth? A movable host of metaphors, metonymies, and; anthropomorphisms: in short, a sum of human relations which have been poetically and rhetorically intensified, transferred, and embellished, and which, after long usage, seem to a people to be fixed, canonical, and binding. Truths are illusions which we have forgotten are illusions- they are metaphors that have become worn out and have been drained of sensuous force, coins which have lost their embossing and are now considered as metal and no longer as coins.

On Truth and Lies in a Nonmoral Sense,  Friedrich Nietzsche 1873

Metaphors are themselves the aptest and clearest mode of expressing much in little. No other form of speech will convey so much thought in so few words. They often compress into a few words what would else require as many sentences. But even such condensations of meaning did not—so it appears—always answer Shakespeare's purpose: he sometimes does hardly more than suggest metaphors, throwing off several of them in quick succession...Here we have a thick-coming series of punning metaphors, all merely suggested. So Brutus, when hunting after reasons for killing Cæsar:

It is the bright day that brings forth the adder.

Here the metaphor suggested is, that the sunshine of kingly power will develop a venomous serpent in the hitherto noble Julius.

From Shakespeare: His Life, Art, and Characters, Volume I. Henry Norman Hudson, New York: Ginn and Co., 1872

As an instance of the simile and the metaphor together, take the following from King Lear, iv. 3, where the Gentleman describes to Kent the behaviour of Cordelia on hearing of her father's condition:

                                     You have seen
Sunshine and rain at once; her smiles and tears
Were like: a better way,—those happy smilets
That play'd on her ripe lip seem'd not to know
What guests were in her eyes which parted thence
As pearls from diamonds dropp'd.

William Shakespeare

From Shakespeare: His Life, Art, and Characters, Volume I. Henry Norman Hudson, New York: Ginn and Co., 1872

Similes: 1.) Sunshine and rain like smiles and tears 2.) parted thence As pearls from diamonds dropp'd

Metaphors: 1.) —those happy smilets That play'd on her ripe lip 2.) What guests were in her eyes

...I ought to add that a simile is sometimes merely suggested or implied; as in these lines from Wordsworth:

What is friendship?—do not trust her,
Nor the vows which she has made;
Diamonds dart their brightest lustre
From a palsy-shaken head.

From Shakespeare: His Life, Art, and Characters, Volume I. Henry Norman Hudson, New York: Ginn and Co., 1872

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In today's music:

The latest technique of rappers is the use of implied similes. Here is the way you can create your own.

1. Create a simile. A statement comparing two ideas similar to each other with the use of words "like" or "as."
2. Remove "like" or "as" from the simile.
3. Give a detail that conveys the idea more directly.

For example:
"I got you begging like a dog." This is a normal simile.
"I got you begging, come here Lassie." This is an implied simile. The listener has to put the "like" in order to make the connection between the ideas. And "Lassie" is a more detailed image of dog than just saying dog.

From The Emcee Mind

Now a simile, as the name imports, is a comparison of two or more things, more or less unlike in themselves, for the purpose of illustration. The thing illustrated and the thing that illustrates are, so to speak, laid alongside each other, that the less known may be made more intelligible by the light of that which is known better. Here the two parts are kept quite distinct, and a sort of parallel run between them. And the actions or the qualities of the two things stand apart, each on their own side of the parallel, those of neither being ascribed to the other.

In a metaphor, on the other hand, the two parts, instead of lying side by side, are drawn together and incorporated into one. The idea and the image, the thought and the illustration, are not kept distinct, but the idea is incarnated in the image, so that the image bears the same relation to the idea as the body does to the soul. In other words, the two parts are completely identified, their qualities interfused and interpenetrating, so that they become one. Thus a metaphor proceeds by ascribing to a given object certain actions or qualities which are not literally true of that object, and which have in reference to it only the truth of analogy.

Shakespeare: His Life, Art, and Characters, Volume I. Henry Norman Hudson, New York: Ginn and Co., 1872