Metadiscourse markers are used as one of the tools which make writing more effective in social environment and are regarded as one of the most important features in communication among people for expressing the information through different linguistic expressions with cohesive and logical constructions. Accordingly, the present study aimed to identify interactive and interactional metadiscourse in a targeted sample of 100 English research articles written by Iranian writers utilizing Hyland's taxonomy. The sample included the discussion sections of randomly selected articles with 70000 running words published between 2010 and 2016. The overall findings disclosed that, in interactive metadiscourse category, the use of transitions, frame markers, and evidentials in social science articles were more frequent than those in medical science texts. The results further revealed that the use of endophoric markers and code glosses were almost the same. In interactional metadiscourse corpora, however, the findings demonstrated that writers used hedges, boosters, and self-mentions more frequently in medical science articles compared to those in social sciences. Comparatively, the discussion sections in social science texts contained a higher percentage of engagement markers. It was also found out that there was no significant difference in the use of attitude markers in both disciplines. Notably, the social science authors seemingly preferred to employ interactive metadiscourse markers more, while the medical science authors used interactional metadiscourse markers more frequently in their research articles.