Non-linear MHD simulations of edge localized modes (ELMs) show features in qualitative agreement with the experimental observations such as the formation and speed of filaments, features in the radial profiles and the fine structure observed in the power deposition profiles at the divertor target. The density perturbation predominantly follows the ballooning mode convection cells leading to density filaments. The temperature perturbation, due to the large parallel conduction, follows the magnetic field perturbation. Simulations of pellets injected in the H-mode pedestal show that the high pressure in the high density plasmoid can become large enough to drive ballooning type modes forming a single helical structure located at the pellet (plasmoid) position.