The aim of this study is to explore how tertiary science students' use of metaphors in their popular science article writing may influence their understanding of subject matter. For this purpose, six popular articles written by students in physics or geology were analysed by means of a close textual analysis and a metaphor analysis. In addition, semi-structured interviews were conducted with the students. The articles showed variation regarding the occurrence of active (non-conventional) metaphors, and metaphorical concepts, i.e. metaphors relating to a common theme. In addition, the interviews indicated that students using active metaphors and metaphorical concepts reflected more actively upon their use of metaphors. These students also discussed the possible relationship between subject understanding and creation of metaphors in terms of conceptual blending. The study suggests that students' process of creating metaphorical concepts could be described and visualised through integrated networks of conceptual blending. Altogether, the study argues for using conceptual blending as a tool for monitoring and encouraging the use of adequate metaphorical concepts, thereby facilitating students' opportunities of understanding and influencing the learning of science.