In order to overcome the difficulties that occur when ultrasonic waves excited by mechanical vibration method applied to metallurgical processes of materials, two electromagnetic methods are proposed to generate intense ultrasonic waves directly in liquid metal in this study. One is the simultaneous imposition of a high frequency electrical current and a static magnetic field; the other is that of a high frequency magnetic field and a static one. A mathematical model based on compressible fluid dynamics and electromagnetic fields theory has been developed to derive the pressure distribution of the generated waves in a metal. It is show that the intensities of the electromagnetic ultrasonic waves are proportional to the product of the static magnetic field and the alternating current of the static and alternating magnetic fields respectively. And the frequency is the same with that of the imposed electromagnetic force. On basis of the theoretical analysis, the pressure changes in a liquid gallium were examined by a pressure transducer under different conditions. The observed results approximately agreed with the prediction derived from the theoretical analysis and calculations. This study shows that electromagnetic ultrasonic waves can be generated in a liquid metal by imposing a high frequency force locally on it and these waves can be used in the refining and solidifying processes of metals.