Nanocavities - typically a few nm to a few tens of nm in size - are often observed in metals, for example in high-temperature applications due to the condensation of vacancies or in metal alloys used in nuclear reactors due to irradiation. The presence of these nanocavities degrades the mechanical behaviour of materials and contributes to fracture. It is therefore necessary to determine the physical mechanisms associated with the behaviour of these nanocavities under mechanical loading and to obtain homogenised models describing the macroscopic behaviour of these nanoporous materials. The results available in the literature remain limited to date, particularly with regard to the representativeness of the simulations carried out and the models proposed for the applications of interest. This includes for example considering crystal defects surrounding the cavities, the effect of cyclic loading and the localisation of nanocavities at grain boundaries. The objectives of this thesis are therefore to determine the behaviour of nanocavities under mechanical loading and the associated physical mechanisms by considering realistic situations with respect to applications, to develop physically-based analytical models to describe the behaviour of nanocavities under mechanical loading, and finally to propose homogenised models adapted to nanocavities that can be used to simulate the failure by growth and coalescence of cavities. The targeted applications are those related to metal alloys under irradiation, but the elements of understanding obtained and the models developed could be used in a broader context. In order to achieve these objectives, Molecular Dynamics (MD) simulations will be performed, analysed from the elastic theory of dislocations and used to propose relevant homogenised models for nanoporous materials.