The talk summarizes general features of mechanisms that generate neutrino mass. The impact of current neutrino data on models for lepton mixing is discussed. Typical examples for new physics in neutrino experiments are given. A general prediction of almost all mechanisms for neutrino mass is the presence of neutrinoless double beta decay. The physics potential of this process is presented, both in the standard approach of light Majorana neutrino exchange, as well as in non-standard scenarios.