The present work relates to the investigation of the basic oxidation characteristics of iron and aluminium nanoparticles as well as the feasibility of their combustion under both Internal Combustion Engine (ICE)-like and real engine conditions. Based on a series of proof-of-concept experiments, combustion was found to be feasible taking place in a controllable way and bearing similarities to the respective case of conventional fuels. These studies were complimented by relevant in-situ and ex-situ/post-analysis, in order to elaborate the fundamental phenomena occurring during combustion as well as the extent and ‘quality’ of the process. The oxidation mechanisms of the two metallic fuels appear different and -as expected- the energy release during combustion of aluminium is significantly higher than that released in the case of iron. The peak gas temperatures recorded during combustion of iron under engine-like and real engine conditions indicate that the NOx formation threshold is not reached. Combustion of aluminium yields substantially higher peak combustion temperatures and thus it is likely that is accompanied by NOx emissions. In addition, the experimental results provided indication that the approach of Exhaust Gas Recirculation (EGR) could be an efficient means of controlling the combustion process.