Metaphor of modality in the Hallidayan linguistic framework is manifested through a transition from implicit modal expressions to explicit modal expressions, encompassing metaphor of modalization and metaphor of modulation. This article conducts a corpus-based investigation to examine the prevalence of metaphors of modalization in English academic writing. The study, which relies on data from the British National Corpus (BNC), reveals that modal expressions are more frequently used in less technical texts (i.e., in spoken texts rather than in written texts with regard to mode, in fiction texts rather than in academic texts with regard to genre, and in hard science texts rather than in soft science texts with regard to discipline). Furthermore, explicit subjective and explicit objective modal expressions exhibit opposite distribution patterns across modes, genres, and academic disciplines. Based on this general distribution pattern, this study then examines three distinct groups of PhD dissertations. It becomes evident that Chinese English as a Foreign Language (EFL) writers employ significantly fewer subjective projecting clauses compared to proficient native English writers in their academic writing. This difference arises from the rigorous training Chinese EFL learners receive, emphasizing the avoidance of authorial identity in academic writing. This study hereby concludes that while English academic writing may be becoming less formal, author involvement should not be encouraged in relatively more technical academic texts.