Metadiscourse refers to aspects of a text, which explicitly organize the discourse, engage the audience and signal the writer's attitude. This paper, first of all, explains the concept, function and categories of metadiscourse, and then discusses the relationship between the use of metadiscourse and the quality of writing. It agrees that now the key word is the appropriate or effective use of metadiscourse. It is the quality, not the quantity, of the metadiscourse used that helps create a successful piece of writing. Finally, it introduces some experimental attempts on the teaching of metadiscourse in classroom with expectations of improving the quality of writing.