This quotation expresses a metaphor because the world is not literally a stage, and most humans are not literally actors and actresses playing roles. By asserting that the world is a stage, Shakespeare uses points of comparison between the world and a stage to convey an understanding about the mechanics of the world and the behavior of the people within it.

The word metaphor itself is a metaphor, coming from a Greek term meaning "transference (of ownership)". The user of a metaphor alters the reference of the word, "carrying" it from one semantic "realm" to another. The new meaning of the word might be derived from an analogy between the two semantic realms, but also from other reasons such as the distortion of the semantic realm - for example in sarcasm.

Metaphor is distinct from metonymy, both constituting two fundamental modes of thought. Metaphor works by bringing together concepts from different conceptual domains, whereas metonymy uses one element from a given domain to refer to another closely related element. A metaphor creates new links between otherwise distinct conceptual domains, whereas a metonymy relies on pre-existent links within them.

A mixed metaphor is a metaphor that leaps from one identification to a second inconsistent with the first, e.g.:

I smell a rat [...] but I'll nip him in the bud" — Irish politician Boyle Roche

If we can hit that bull's-eye then the rest of the dominoes will fall like a house of cards... Checkmate.

An extended metaphor, or conceit, sets up a principal subject with several subsidiary subjects or comparisons. In the above quote from As You Like It, the world is first described as a stage and then the subsidiary subjects men and women are further described in the same context.

Metaphor can serve as a device for persuading an audience of the user's argument or thesis, the so-called rhetorical metaphor.

Metaphors can be implied and extended throughout pieces of literature.

The term metaphor is used to describe more basic or general aspects of experience and cognition:

Lakoff and Johnson greatly contributed to establishing the importance of conceptual metaphor as a framework for thinking in language, leading scholars to investigate the original ways in which writers used novel metaphors and question the fundamental frameworks of thinking in conceptual metaphors.

James W. Underhill, in Creating Worldviews: Ideology, Metaphor & Language (Edinburgh UP), considers the way individual speech adopts and reinforces certain metaphoric paradigms. This involves a critique of both communist and fascist discourse. Underhill's studies are situated in Czech and German, which allows him to demonstrate the ways individuals are thinking both within and resisting the modes by which ideologies seek to appropriate key concepts such as "the people", "the state", "history", and "struggle".

Though metaphors can be considered to be "in" language, Underhill's chapter on French, English and ethnolinguistics demonstrates that we cannot conceive of language or languages in anything other than metaphoric terms.