This paper investigates audience type and metaphor strategy of the writing in science area. the audience type is divided into 'non-socialized audience', 'pre-socialized audience', 'socialized audience', 'post-socialized audience'. This division is connected to the relationship of audience and discourse community. The audience type effect on the strategies of content construction. This paper focused on metaphor strategy among them of content construction, and proved it's function as the strategies of content construction. The function of metaphor strategy follows : promoting content comprehension to 'non-socialized audience', learning discourse conventions and assumptions to 'pre-socialized audience', building and explaining the theories to 'socialized audience', criticizing and interpreting newly the theories to 'post-socialized audience'. This paper's results are utilized to teach informative writing. The first, guiding the student writer to aware audience in writing context, the second teaching to use the strategies of content construction according to audience type.