The different uses of metaphors are to evoke certain images and feelings, to send an implied message, and to represent things or ideas. Writers of all kinds have always used metaphors to add meaning to their writing that goes beyond the written word itself. Musicians, politicians, and other public speakers also use metaphors to enhance the meaning of their words and often use them to create an image. Metaphors are also an important part of everyday life as humans rely on metaphors to describe and make sense of the world around them.
For as long as literature and poetry have existed, writers have used metaphors to paint pictures for their readers. These uses of metaphors evoke emotion in the reader and create an image that goes beyond the literal meaning of the words. For example, a man described as a dog brings up a very different image than one described as a bull. When considering the uses of metaphors, the written word is probably what most people think of first, as poets and authors are well known for using colorful metaphors to create a scene for their readers.
One of the more subtle uses of metaphors is to send an implied message or to create a persona through the use of words. This tends to be more common with spoken words like when a politician campaigns, a public speaker makes a speech, or a musician sings a song. The words that these people choose will ultimately send a message to their audience. An example of this would be a politician calling himself "the hand of justice" or promising "to clean up" a city. This same principle is also used in marketing and advertising to build an image for a brand that people will relate to and remember.
In a sense, all words are metaphors for the real life objects they represent, and several of the uses of metaphors involve everyday language that most people never even recognize as metaphors. Many common phrases and colloquialisms are really metaphors that have become frequently used to express an idea. The presence of technology has necessitated the use of symbolic metaphors for things in the cyber world so that they seem more relevant to the general public. Examples of this are the "folders" and "desktop" on a personal computer or the "shopping cart" at an online store. Assigning something tangible to an intangible idea puts it in a context that is easier to relate to.