In consideration of the factor that the energy of the induced current on a scattering object excited by a plane wave with a Gaussian pulse almost all concentrates on a finite time and frequency-domain, by expanding the response in time with Laguerre function, a corresponding frequency-domain response is attained by using Fourier transform. According to the characters of Fourier transform, the low-frequency and high-frequency responses determine the late-time and early-time responses respectively. In this paper, the early-time and low-frequency responses are generated through the use of a time-and-frequency hybrid method including MOT and MOM and they are mutually complementary and contain all the necessary information. So the whole response can be attained by simultaneous extrapolation in time and frequency domains. The electromagnetic scattering responses in the time and frequency domains of the ideal metal conductors are calculated and analyzed by using this method.