Metadiscourse is a tool for writers to guide and interact with readers through texts. Yet in most student texts, one of the points lacking is the interaction between writers and readers. In this study, frequency and type of interactive and interactional metadiscourse features were explored via students' research-based essays based on Hyland's metadiscourse taxonomy. Additionally, the students' English Vocabulary Profile (EVP), lexical diversity, lexical density, and readability features of the texts in the corpus were scrutinized, which serve as an indicator of writing quality. Finally, the relationship of metadiscourse use with students' writing performance, lexical diversity, lexical density, and readability was explored through statistical measures. Findings show that following explicit metadiscourse instruction, students' research-based essays included more interactive metadiscourse than interactional metadiscourse, indicating that the students were dealing with more textual features, such as coherence, than interactional metadiscourse. Apart from findings regarding EVP such as lexical diversity, lexical density, and readability features, a positive relationship was explored between metadiscourse use and writing performance, lexical components, and textual features. It is concluded that metadiscourse should be integrated into the writing syllabus since it has a positive relationship with students' use of academic vocabulary in their essays.