This paper proposes a method for nonlinear damage localization in the beam and plate structures with nonlinear vibration modulation of ultrasonic-guided waves. In the proposed technique, the damaged metal beam and plate are designed to form a cantilever structure. A magnetic system is also involved in the model to control the dynamics of this cantilever structure. The oscillation model exhibits nonlinear vibration that is used to modulate the ultrasonic-guided waves. By utilizing a synchronous phase-locked demodulation technique, the nonlinear reflection profile from the nonlinear scatterer is extracted and employed for localizing the nonlinear damage. The proposed technique has the merits of being perceptive to nonlinear scattering sources, without requiring a damage-free signal, and with enhanced performance at a wide range of frequencies. These merits have been experimentally validated by localizing fatigue crack in a metal beam and imaging simulated contact defect in a metal plate. The proposed technique is suitable in the structural health monitoring (SHM) for nonlinear damage localization in the absence of a baseline signal by ultrasonic-guided waves.