Short answer: in the simile vs metaphor question, the difference is how openly the comparison is made. A simile says one thing is like or as another: "He fought like a lion." A metaphor drops the comparison word and says one thing is the other, or simply treats it that way: "He was a lion in the fight." Both compare two unlike things. The more useful question for a writer is which one to choose, and that depends on how much of the comparison you want the reader to accept. Below: the definitions, the edge cases, and a decision table.
The definitions, in plain terms
A simile is a figure of speech that compares two unlike things with an explicit signal, usually "like" or "as." "Her voice was like gravel." "Busy as a bee." The signal tells the reader that this is a comparison, not a claim of fact.
A metaphor makes the same kind of comparison without the signal. It speaks of one thing in terms of another. "Her voice was gravel." "The classroom was a zoo." The reader is trusted to know the statement is not literal.
The words themselves describe the move. The Online Etymology Dictionary, read on October 2, 2026, traces simile to Latin simile, "a like thing; a comparison, likeness, parallel," and dates it in English to the late 14th century. Its entry for metaphor traces that word through French and Latin to Greek metaphora, "a transfer," literally "a carrying over," from meta "over, across" and pherein "to carry, bear." It dates metaphor in English to the late 15th century. A simile points at a likeness; a metaphor carries a name across from one thing to another.
Register and region: both terms are standard in the US and the UK, and they are used the same way in classrooms, style guides and literary criticism.
Simile vs metaphor: the quick comparison
| Simile | Metaphor | |
|---|---|---|
| What it says | A is like B | A is B, or A acts as B would |
| Signal word | like, as, as if, as though, resembles | none needed |
| Example | "The lake was like glass." | "The lake was glass." |
| How it reads | Open, explained, a little cautious | Direct, compressed, more assertive |
| Can it run for a paragraph? | Yes, as an extended or "epic" simile | Yes, as an extended metaphor |
| Main risk | Can feel wordy or stock ("cold as ice") | Can be misread, or collide with a second image |
Aristotle saw them as nearly the same thing
The argument over which device is better is older than English. Book III of Aristotle's Rhetoric, in W. Rhys Roberts's translation at the MIT Internet Classics Archive (read October 2, 2026), opens Part 4 with: "The Simile also is a metaphor; the difference is but slight." His example is Homer's Achilles. "Leapt on the foe as a lion" is a simile; "the lion leapt" is a metaphor.
Aristotle also ranked them. In Part 10 he calls the simile "a metaphor, differing from it only in the way it is put; and just because it is longer it is less attractive." In Part 4 he adds that similes are useful in prose "but not often, since they are of the nature of poetry."
That view still has followers. Robert Lee Brewer, writing in Writer's Digest under the title "Simile vs. Metaphor: Smackdown!" (read October 2, 2026), prefers metaphors in poetry for their economy and argues that "My heart is a train is a stronger statement than my heart is like a train." He also concedes the other side: "Not every this is a that," and similes, he writes, are very useful in communication.
Popular writing guides still split on which device is "stronger." Some call the metaphor the more forceful comparison; others say the simile makes the clearer connection. Both camps describe something real. They are measuring different things: force on one side, clarity on the other.
Is a simile a kind of metaphor?
It depends on whom you ask. Aristotle treated the simile as a metaphor with an extra word. Many classroom definitions present them as two separate devices, side by side, told apart by "like" or "as." Some guides go further and call metaphor the broad category, with simile as one type inside it.
For a writer, the answer changes very little. What matters is the surface: whether the comparison is announced or not. That surface is what the reader experiences, and it is what the rest of this page is about.
Edge cases: when "like" does not make a simile
The "look for like or as" test works most of the time, but it has three blind spots.
1. Literal comparisons are not similes. "She looks like her mother" compares two things of the same kind, so it is a plain comparison, not a figure of speech. A simile needs two unlike things: "She moved like a cat."
2. Similes can use other signals. "As if," "as though" and "resembles" can all carry a simile. "He ran as if the floor were on fire" has no "like," but it is still a simile.
3. Metaphors do not need "is." A verb can carry the whole image: "She sailed through the exam," "the news hammered his confidence." A noun phrase can too: "a mountain of paperwork," "a sea of faces." None of these says "X is Y," and all of them are metaphors.
A handy test: if you can insert "like" without changing the meaning, and the result compares unlike things, you have a metaphor that could also be a simile. "The classroom was a zoo" becomes "the classroom was like a zoo."
When a simile is the better tool
A simile earns its extra word when the comparison needs a limit or an explanation.
- The likeness is partial. "The office was like a sauna" says one thing: it was hot. "The office was a sauna" invites the reader to wonder what else about it was sauna-like. When only one quality transfers, "like" fences the comparison in.
- The comparison needs a tail. A simile can carry an explaining clause. Aristotle quotes Androtion saying that Idrieus "was like a terrier let off the chain, that flies at you and bites you." The clause after "terrier" tells you exactly which part of the terrier is meant.
- The image is unfamiliar. If the reader may not know the second thing well, the signal word warns them a comparison is coming and buys a moment to process it.
- The speaker is unsure. In fiction, "it looked like smoke" is what a character says when they are not certain. "It was smoke" is a statement of fact. Similes, especially with "as if" or "seemed," let a narrator hedge.
- The text is practical, or the reader is learning English. In instructions, business email or ESL material, a simile is less likely than a metaphor to be read literally.
When a metaphor is the better tool
A metaphor earns its directness when the comparison should feel like a fact.
- You want force. "Her silence was a wall" lands harder than "her silence was like a wall," which is Brewer's point.
- You want to keep the image going. A metaphor can run across several sentences ("the wall had no door; he walked its length every evening") without repeating "like." An extended simile is possible, but each new "like" reminds the reader that it is only a comparison.
- The image lives in an action. Many strong metaphors are verbs: "the crowd surged," "the rumor leaked." There is no simile version that is as short.
- The image is already familiar. "A sea of faces" needs no warning label.
- Space is tight. In headlines, titles and slogans, "is" beats "is like."
The decision table
| Your situation | Better choice | Why |
|---|---|---|
| Only one quality transfers (heat, speed, color) | Simile | "Like" limits the comparison to that quality |
| You want to explain the comparison in the same sentence | Simile | A simile can carry a "that" or "who" clause |
| The second image is unusual or technical | Simile | The signal word prepares the reader |
| A character or narrator is uncertain | Simile ("as if," "seemed like") | It keeps the claim tentative |
| Business, instructional or ESL writing | Simile, or no figure at all | Lower risk of a literal reading |
| You want maximum force in few words | Metaphor | No hedge word dilutes it |
| The image continues for several sentences | Metaphor | It extends without a repeated "like" |
| The comparison is an action | Metaphor (in the verb) | "Surged," "leaked," "hammered" do it in one word |
| The image is a stock one ("cold as ice") | Neither: rewrite | Readers skim familiar similes; a fresh detail does more |
This table is our guidance, built from the arguments above. No dictionary lays it down as a rule, and a good writer will find exceptions.
Turning one into the other
Most similes convert to metaphors by deleting the signal word, and most noun metaphors convert back by adding it. Try it on your own sentences and read both versions aloud.
- Simile: "The highway was like a parking lot." Metaphor: "The highway was a parking lot."
- Simile: "His words cut like a knife." Metaphor: "His words were a knife." Or, through the verb alone: "His words cut."
- Metaphor: "Time is a thief." Simile: "Time is like a thief."
Notice the third pair. "Like a thief" sounds weaker because the original was a claim about time. When a metaphor is making a claim, its simile version tends to sound as if it is backing away from that claim. That is a useful signal: if the simile version sounds timid, the metaphor was probably the right call.
One trap to watch: if you convert several similes into metaphors in the same paragraph, two images can end up colliding, a wall in one sentence and a river in the next. Read the converted passage as a whole, not line by line.
Where idioms fit
Many idioms are metaphors that froze into fixed phrases. "Break the ice" began as a picture of clearing a route through ice; our page on the break the ice origin traces how that picture became one about easing a conversation. Others are images nobody can fully explain any more, which is the situation with raining cats and dogs, whose origin the references have not settled.
This matters for the simile vs metaphor choice in one practical way. When you use an idiom or a stock simile, you are borrowing someone else's comparison, and readers have met it many times. It will be understood, but it will rarely be noticed. If you want the reader to see the comparison, make your own. For how phrase histories like these are traced in the first place, see our explainer on where idioms come from.
Frequently asked questions
What is the main difference between a simile and a metaphor?
A simile announces the comparison with a signal word such as "like" or "as" ("fast as lightning"). A metaphor makes the comparison without the signal word ("he was lightning on the field").
Is a metaphor stronger than a simile?
Often, but not always. Aristotle, in the Rhetoric, found the simile less attractive because it is longer, and many writing teachers agree that a metaphor is more forceful. A simile is the clearer choice when only one quality transfers or the comparison needs explaining.
Is "as busy as a bee" a simile or a metaphor?
It is a simile, because the "as … as" pattern signals the comparison. It is also a stock phrase, so in fresh writing a more specific image usually works better.
Can one sentence contain both a simile and a metaphor?
Yes. "The city was a furnace, and the asphalt shimmered like water" has a metaphor followed by a simile. Keep the two images compatible so they do not clash.
Do all similes use "like" or "as"?
No. "As if," "as though" and "resembles" can also introduce a simile, as long as the comparison is between two unlike things.