The Function of a Metaphor and Simile

"Because writing is an extension of reading, and because the students have been reading all their lives, it is understandable that the two activities might blur somewhat in their minds. Although it is certainly a good thing that their writing is informed by their reading -indeed, at the most basic level they wouldn't be able to write anything at all if it weren't-it has its dangers. The creation of metaphors and similes, for instance. "The boy hopped up and down' writes a bright student whose intuition, sense of rhythm and experience as a reader tell her a metaphor or simile is needed to complete the sentence, "like beads of water on a hot frying pan?' In the rush to meet the demands of intuition and rhythm she has written a weak metaphor. She has forgotten the function of the device, which is to make something crystal clear, to reduce to essence. She has tried to amplify, to add on, rather than reduce." (Frank Conroy from Dogs Bark, but the Caravan Rolls On)