The purpose of this study was to examine the extent to which preservice elementary teachers were able to construct viable scientific models with a computer-modeling tool, namely Model-It, and design a science lesson with models. The results of the study showed that (a) Model-It, through its scaffolds (i.e., Plan, Build, and Test modes), enabled the majority of preservice teachers to build models that were structurally correct, (b) participants' models were structurally correct but simplistic, and (c) 65% of the participants preferred to teach science using the explorative modeling method, 27% the expressive method, and only 8% both the explorative and the expressive methods. In essence, Model-It effectively scaffolded preservice teachers' first modeling experiences and enabled them to quickly build and test their models. It is, however, recognized that systematic efforts need to be undertaken in teacher education departments to adequately prepare prospective teachers to teach science through computer models.