A system for monitoring an area includes a processor and an electromagnetic radiation source in communication with the processor. The electromagnetic radiation source is configured to emit radiation to heat a metallic object that is in or carried by a target. The system also includes an array of temperature sensors in communication with the processor, where the array of temperature sensors is configured to detect a first temperature associated with the target and a second temperature associated with the target. The first temperature is detected prior to emission of the radiation and the second temperature is detected subsequent to emission of the radiation. The processor is also configured to determine whether to trigger an alert based at least in part on a difference between the first temperature and the second temperature.