The purpose of using figurative language, as opposed to literal language, is as follows: the use of figurative speech allows the reader to imagine what the author means when he writes a sentence or a statement. Figurative speech adds strength and depth to an authored work. A good example of figurative speech is the following:
The literal version is: The sun rose at 4:45 am.
The figurative version could be something along the lines of:
The girl stood and watched as a golden globe rose out of the sea.