In spite of a lack of consensus about the nature of scientific models, the role of models and modelling are well established in the practice of science. Students who participate in developing, validating, deploying, and refining models are engaged in authentic scientific practices. Modelling instruction (MI) was developed to promote the role of models and modelling in introductory university physics classes. MI for university physics is founded on the basis of two theoretical foundations, modelling theory of science and modelling theory of instruction. We claim that the translation of these theories into classroom practice supports learning in science. We substantiate this claim by first describing how these theories establish complementary cycles of content development and student participation. Then we provide evidence of these interacting cycles by analysing the development of a conceptual model in a MI university physics class using video data. The video data we present includes students developing a scientific conceptual model first in a small student group and a later in the full class. We argue that the integration of the theoretical components underlying MI are key supports in providing the opportunity for students to develop conceptual models and engage in the practice of doing physics. © 2018 European Physical Society.