Grammatical metaphor studies: historical review and outlook

Grammatical metaphor, a significant theoretical innovation within Systemic Functional Linguistics (SFL), extends meaning realization from the lexical to the grammatical stratum, providing a powerful framework for analyzing abstraction and technicality in academic and scientific discourse. Adopting a methodology of combining systematic retrieval with thematic analysis, this article reviews 293 primary studies on grammatical metaphor within SFL since Halliday initial proposal. We first trace Halliday's three-stage theoretical development of grammatical metaphor. Subsequently, our thematic synthesis reveals predominant sub-themes within two major streams: theoretical development (encompassing semantic and characteristic discussion, interdisciplinary dialogues with Cognitive Linguistics and educational sociology, and typological debates) and practical application (covering language teaching, textual analysis, and translation studies). Based on the synthesis, we propose four key directions for future research: expanding the linguistic scope, broadening the population of second language learners, establishing identification criteria for grammatical metaphor in non-English languages, and delineating demetaphorization. The findings of this review offer valuable theoretical references for linguists seeking to refine grammatical metaphor theory, as well as practical guidance for language teachers and curriculum developers aiming to foster learners' academic literacy. Moreover, the proposed future directions are intended to inspire researchers to explore cross-linguistic and interdisciplinary dimensions, ultimately facilitating a more inclusive and methodologically robust field of grammatical metaphor studies.