Contributions to the field of cellular energy metabolism have been dominated by biochemistry. Over the past decade, however, several physics-based approaches have been introduced. Oscillations are an intrinsic aspect of all living systems, from fluctuating substrate levels within cells to changes in electrical potential across membranes. Utilising physics-based approaches to analyse these time-dependent signals reveals pockets of predictable stability. By embracing the nonlinear, time-varying and open nature of cellular dynamics, new network-based approaches to modelling cells are emerging, capable of effectively replicating measured time-series data. These new approaches promise to bring greater comprehension of how various illnesses affect the cells, and indeed, to novel treatments or diagnostic methods.