Although the use of Grammatical Metaphor (GM) has been regarded as one of the representative features of academic writing in the framework of Systemic Functional Linguistics (SFL), not many studies have explored its role in second or foreign language writers’ writing quality. This study aimed to discover the potential relationship between GM development and argumentative writing quality of advanced Korean EFL learners, while controlling for their overall language proficiency and reading comprehension ability. The findings from this study unveiled significant contribution of the use of both premature and mature GM and also identified transcategorization as the specific GM that has relatively stronger predictability of writing quality. The results from current research yield meaningful pedagogical implications for writing instruction in Korean EFL contexts.

Nominalization is regarded as one of the most salient features of native speakers’ texts according to studies investigating academic discourse. Systemic functional linguistics (SFL) identifies grammatical metaphor, which is often identical to nominalization as a key linguistic resource for achieving matured writing. This study examines Korean high school EFL learners’ deployment of grammatical metaphor (GM) by the method of a text analysis and attempts to demonstrate what extent learners from two different proficiency levels use GM in terms of occurrence of nominalization and the nominal group. Six argumentative texts were chosen from the database of over 1200 texts after a genre-based instruction of a semester. The outcome of the study shows that more skilled students used more GM and nominal groups than less skilled students do. It reveals the effect of GM use in writing quality and the probability of GM in pedagogy and assessment of secondary school writing in Korea. Therefore, this research for GM based on SFL is meaningful in the relevant area as the functional role of language is regarded as central.