Metadiscourse refer to linguistic resources that are used to refer to the act and the context of writing about some subject matter. Study of metadiscourse provides a gateway for understanding interactional features of texts or speech, looking beyond the ideational dimension of texts at how writers characterize the world and function interpersonally. The ability of writers to use metadiscourse effectively, to control the level of personality in their texts by offering a credible representation of themselves and their ideas, is seen as a defining feature of successful writing (Hyland, 2008). This paper provides a literature review of the theories in modelling metadiscourse and the studies investigating metadiscourse for the past 15 years, and propose future research directions based on the review.