In science teaching, metaphors are important tools for understanding meaningful learning and conceptual formation by the help of daily life language. This study aims to evaluate how the concepts of heat, temperature and energy are perceived by students in secondary school science classes and how the perceptions of these concepts vary in terms of metaphors depending on grade level (5th, 6th, 7th and 8th grades). The study group of the present research consists of 226 students selected from 5th, 6th, 7th and 8th graders through criterion sampling method. The descriptive method was used in the study and the data was collected by metaphor questionnaire. According to the findings, 176 metaphors were generated by students under four categories "formal/scientific metaphors", "Abstract metaphors", "Environmental/daily metaphors" and "misconception metaphors". When the findings were examined, it was seen that though there were some misconception detected about the concepts of heat, temperature and energy, conceptual changes in the other three categories vary depending on grade level. This variety needs to be discussed in relation to cognitive development and daily life. Some suggestions were made about the place and importance of metaphors in concept teaching for researchers and practitioners.