From a Systemic Functional perspective, Grammatical Metaphor (GM) as is taken to be a chief driving force in the discourse of different genres, an important adult language machinery for ideational meanings to be semantically cross-mapped and realized through a different form in the stratum of the lexico-grammar, in order to convey changed meanings and tinker with the discursive flow and development of text in real time, mainly through nominalization of adjectives and verbs. Using a number of established works of the English novel as data, this study draws upon the author’s previous model for the categories of GM used in modern prose fiction, with the main focus placed on one of the six categories, Prepositional GM (PGM). PGM figures with a very high frequency in fiction and occurs when a GM is preceded by a preposition. This study finds that the language of prose fiction in English deploys some of these PGMsin either of two different meaning sof the adverbial, varying according to context. Again, as seen to be the hallmark of GM by many, GM is found to open up vast ideational meaning potentials in the semantics stratum, from which the lexico-grammar makes choices according to context and intended meaning. As argued elsewhere in the literature and here, and as backed up by the author’s own experience of the advanced teaching of writing and reading, broadened understanding of GM is a critically important component to writing instruction and its effectiveness, as seen in the large-scale horizons and agendas for effective teaching of English as a Foreign Language in Iran and beyond.