An apparatus and a method for detecting a metal foreign matter in a wireless charging system, and a device are provided. The apparatus includes a phase-lock control module, an excitation module, a resonance module, a signal collection module, and a determining module. The phase-lock control module is configured to: adjust a frequency of a first signal and output the first signal to the excitation module and the determining module. The excitation module is configured to: generate a second signal based on the first signal, and output the second signal to the resonance module. The resonance module is configured to output the third signal to the signal collection module under excitation of the second signal. The determining module is configured to determine whether there is a metal foreign matter in an area of the target coil.