Recent researches on metamaterials (MMs) demonstrated that a nonlinear MM exhibits a rich spatiotemporal dynamics where both linear and nonlinear e®ective properties can be tailored simply. This provides opportunity to explore the new nonlinear optical phenomena in MMs. This contribution reviews the recent advances on nonlinear interaction between electromag- netic wave with MMs, from the fundamental physical models to unique phenomena and conceived novel devices. The physical origins for the typical nonlinear phenomena, such as second-order harmonic generation (SHG), optical parametric ampli¯cation (OPA), four-wave mixing (FWM), optical soliton, self-phase modulation (SPM), and self-focusing in MMs are explained. Several proposals for applications of nonlinear MMs in manipulating light are demonstrated.