This study analyses the evolution of the personal metaphors of 31 science graduates enrolled in a Master's degree course in Secondary Education Teaching during the 2012-13 academic year. The instrument used was an open questionnaire that included asking the participants to make drawings representing the roles of the teacher. Four categories of metaphor were considered: behaviourist/transmissive, cognitivist/constructivist, situative/socio-historical, and self-referential. It was found that most of the prospective teachers were indeed able to conceptualize their roles in the form of metaphors. Comparison of the results before and after the teaching practicum revealed no changes in most of the participants' metaphors and associated models. Instead, these appeared to be firmly set already at the beginning of the Master's course, and remained uninfluenced by either the course or the practicum. Only a minority of the participants showed changes in their metaphors--5 with progressive changes, and 5 with regressive changes.