Monte Carlosimulations can be applied to a wide variety of topics.I will showsome examples like adsorption of particles on surfaces,nanowires andnanoparticles.By means of Monte Carlo simulations and a lattice model, the adsorption of particles on surfaces was studied. Some real systems were modeled, such adsorption of silver on gold surfaces, or different combinations of metals as adsorbate and substrate. On theother hand, some idealized systems of monomers and dimers adsorbed on different kinds of surfaces were simulated and the percolationproperties were studied.Another application of Monte Carlosimulations were the study of nanowires and nanoparticles of severalmetals and alloys. Ab-initio calculations were employed to studysystems related to sutainable energies, like fueel cells andLithium-ion batteries. A combination of ab-initio with Monte Carlomethodsare also employed to study hydrogen adsorption on metalsurfaces.