What is a metaphor vs. simile?

"O my Luve is like a red, red rose" (Burns, "A Red, Red Rose," 1794) is a simile. "All the world's a stage" (Shakespeare, As You Like It, 1599) is a metaphor. The line is the like: a simile names the comparison, a metaphor performs it. The schoolroom version of that rule (the like or as test) works on most sentences, and breaks on three predictable ones: a stretch of figurative description with no is, similes that drop like, and the spoken-English be like idiom that looks like a simile and isn't.

How Do You Tell a Metaphor from a Simile in a Sentence?

The working test has two steps.

Step 1. Does the sentence use like or as to mark the comparison? If yes, you have a simile. "O my Luve is like a red, red rose" (Burns, "A Red, Red Rose," 1794) puts like between the two terms and lets them stay separate.

Step 2. If there is no like or as, look for an implicit identification: X is Y, or X does what Y does. "All the world's a stage, / And all the men and women merely players" (Shakespeare, As You Like It, 1599) collapses the two terms into one. That collapse is the metaphor.

	Simile	Metaphor
Marker word	like or as	none
Shape of the claim	A is like B	A is B
Canonical example	"O my Luve is like a red, red rose" (Burns, "A Red, Red Rose," 1794)	"All the world's a stage" (Shakespeare, As You Like It, 1599)
Felt effect	Acknowledges similarity; the two terms stay visibly separate	Asserts identity; the qualities of B transfer to A

The "like or as" rule clears most cases. Three it doesn't are covered next: extended metaphor without an is, similes that drop like, and the be like idiom that looks like a simile and isn't.

Why Does the "Like or As" Rule Sometimes Fail?

Three cases break the rule.

Extended or implied metaphor without a copula. A metaphor doesn't need an is (the copula, the linking verb that joins subject and predicate). Sylvia Plath's "Metaphors" (1959) opens "I'm a riddle in nine syllables" and then runs nine more lines of figurative self-description, almost none of them using is. The poem is wall-to-wall metaphor; the identification is carried by the rest of the grammar (an elephant, a melon strolling on two tendrils, a means, a stage). A passage of figurative description with no like and no is is still metaphor when the identification is clearly there. The test is whether the figure performs the comparison rather than naming it.

Similes that drop the explicit like. As alone can mark a simile, and it is easier to miss. "Silent as snow," "quick as a hiccup," "thin as gauze." There is no like and no is of identification, but the comparison is still being explicitly marked. Anything in the shape X as Y where as is doing comparison work is a simile.

The be like idiom. In spoken English, "I was like, no way" or "She's like, whatever" is reported speech, not comparison. The like is acting as a quotative particle (it introduces what someone said or thought), not as a marker of similarity. The sentence is doing something closer to "She said, whatever" than to "She is similar to whatever." This idiom looks like a simile on the page and isn't one.

The practitioner's version of the rule, after the three cases: the figure is a simile only when like or as is doing comparison work, not idiom work or quotation work. Everything else with a felt identification between two terms is a metaphor, copula or no copula.

When Should You Reach for a Metaphor Instead of a Simile?

The two figures don't do the same job.

A simile keeps the two terms visibly separate. The reader sees that A is being compared to B; the comparison is on the table, available to weigh. That is what you want when the likeness is partial, when you want the reader to do part of the work, or when an outright identification would overclaim. Joan Didion writes that the Santa Ana wind "blows in" and "people get tense" and the air "smells of resin," and then: "It is hard for me to believe that you can live in any town in Southern California any length of time without coming to feel that the wind is what the place is about." (Didion, Slouching Towards Bethlehem, 1968, "Los Angeles Notebook.") The looseness of like would have given the reader an out; the bare is of metaphor closes the door. Didion's prose tends to reach for the closing-door move because she wants her observation taken as a fact about the place, not a writer's flourish.

A metaphor collapses the two terms. The qualities of B transfer to A wholesale, and the sentence can move on. That is what you want when the figure has to do structural work the sentence can't pause for. "Time is money" (Franklin, "Advice to a Young Tradesman," 1748) is a metaphor because the rest of the essay is built on it; a simile would have left "time" and "money" facing each other instead of welding them into a unit Franklin could spend the rest of the page deploying. Working writers usually reach for metaphor when the figure has to support the next several sentences, and for simile when the comparison is the whole job in this one sentence.

The choice isn't about which is stronger. It's about whether you want the comparison to stay visible (simile) or to vanish into the thing it produced (metaphor). Metaphor has several subtypes built on this same base move (implied, extended, dead, mixed), and each one is a different way of letting the identification do work the sentence can't pause for.

Are There Other Figures That Compare Two Things?

Three neighbors share territory with metaphor and simile, and each has its own test.

Analogy is an extended structural comparison that reasons by ratio. A is to B as C is to D. "A school is to a city what a factory is to an industry" makes a claim about how the parts relate, not just that the parts resemble each other. A metaphor asserts identity; an analogy asserts proportion. The test: can you draw a four-term grid out of the comparison? If yes, you are in analogy territory.

Metonymy is substitution by association, not comparison. "The crown will issue a statement" uses crown for the monarchy because crown and monarchy are connected, not because they are alike. A metaphor compares; metonymy stands in. The test: is the substituted word something the original has, contains, or causes? If yes, metonymy. The line between metaphor and metonymy is the cut between comparison figures and substitution figures, and it is the one most likely to get blurred.

Personification is a sub-form of metaphor: the target of the comparison is human. "The wind whispered" gives the wind a human capacity, which is a metaphorical identification of wind with a speaker. Anything non-human given a human action, feeling, or capacity is personification.

These figures and the metaphor-simile pair sit inside one small family of comparison figures, and the same test logic carries across all of them: find the marker word, find the identification, ask what structural work the figure is doing in the sentence. The closest neighbor for most readers, once metaphor and simile are sorted, is the analogy line.