Students solve problems by developing mental models of the problem. Although these models are many and diverse, a common one used in engineering mechanics education consists of identifying the known and unknown variables, construction of a graphical problem representation, and developing a mathematical model derived from the preceding steps. This is also the case for courses in physics, mechanics, science and electrical circuits. M-MODEL is a computer-based implementation of this approach to problem-solving. It utilizes the visual graphic, variables identification and listing, and mathematical equation mental models as a construct for students to developing STEM problem solving skills. This paper describes how students use M-MODEL to solve problems and its coaching tools. This paper discusses the design objectives, intelligent tutor, and features of M-MODEL as applied to an engineering mechanics course. It also discusses how M-MODEL may be used to encourage students to develop mental model approaches to problem solving. An assessment of M-MODEL is also presented.