The official definition of a metaphor is
A figure of speech in which an expression is used to refer to something that it does not literally denote in order to suggest a similarity.
That is very truthful when one looks at the web and the use of metaphors on that platform.
There, we use pixels as representatives of real world objects to bridge a sense of familiarity between the life on the web and actual life.
In addition, there are several different types of metaphors we use on the web.
- those on a smaller-scale that mimic real-life objects like buttons,
- iconic metaphors which copy real life associations and use them on the web, and
- extended ones where an entire design can revolve around a metaphor.