Metaphor is a linguistic and conceptual structure which has received growing attention in CDA.  A whole approach dedicated to metaphor now exists under the bannar of Critical Metaphor Analysis (Charteris-Black 2004).  According to Charteris-Black, metaphor is 'central to critical discourse analysis since it is concerned forming a coherent view of reality' (2004: 28).   

Critical Metaphor Analysis applies metaphor theory from Cognitive Linguistics.  Here, metaphor is seen as a conceptual structure in which one domain of experience provides the basis for our understanding of another more abstract social domain (Lakoff and Johnson 1980).  These conceptual metaphors are an important part of ideology since they 'provide the cognitive framework for worldview' (Santa Ana 2002: 21).  This worldview, however, is only partial, where conceptual metaphors ‘privilege one understanding of reality over others' (Chilton 1996: 74).

Conceptual metaphors are reflected in, and reproduced by, linguistic metaphors.  Critical analysis of linguistic metaphors in text can therefore reveal underlying ideologies and ideoological reproduction.  Conceptual metaphors, as well as other idealised cognitive models such as frames, can be thought of as the formal structures which discourses take (Hart 2010).