Understanding the processes that shape forest functioning, structure and diversity remains challenging, although an increasing amount of data documents forest systems across scales. Forest models have a long history in assimilating various data and ecological knowledge and can simulate forest dynamics over spatio-temporal scales unreachable by most empirical investigations. Here we describe the trajectories of development different forest modelling communities have followed to demonstrate the leverage that computer models offer for advancing the understanding of forest ecosystems. Using three widely applied but contrasting forest modelling approaches - species distribution models, individual-based models and dynamic global vegetation models - as examples, we show how scientific and technical advances have led models beyond their initial objectives and limitations. We provide an overview of recent model applications on current important ecological topics and pinpoint ten key questions that could, and should, be tackled with forest models in the next decade. This shows that forest models, due to their long history of assimilating empirical knowledge, their iterative and continuous development, and their complementarity, represent an invaluable toolkit to address a wide range of theoretical and applied ecological questions, hence fostering a deeper understanding of forest dynamics, particularly in the context of global change.