Research in metadiscourse has foregrounded the multiple ways in which writers build a relationship with readers through internal discourse. Yet, few studies consider the relationship between the texts writers create and the metalinguistic thinking which informs their decision-making as writers. This paper draws on data from a larger study which sought to address this gap by investigating both the occurrence of metadiscourse in students' writing and their metalinguistic understanding of metadiscourse usage in their own texts. The sample comprised 195 students who wrote argument texts in both L1 Arabic (first language) and L2 English (second language), generating a corpus of 390 texts. Interviews were conducted with a sub-sample of 41 students to determine their metalinguistic thinking. In this paper we focus on "transitions" - the internal devices which mark the steps and connections in the discourse. The analysis evidences a limited metalinguistic understanding of the metadiscoursal function of transitions but a strong understanding of the linking function of transitions. This understanding tends to foreground transitions' textual rather than interpersonal role, emphasising the semantic and ideational. The paper argues that developing students' metalinguistic understanding of this interpersonal role would empower them to make more strategic, informed use of transitions in their own writing.