The equation of characteristics for system of the equations of movement isotropic magnet-elastic media with ideal conductivity is obtained and expressions for velocities of propagation magnet-elastic waves are found. The analysis of influence of a magnetic field on change of values of velocities of propagation of elastic waves for various angles of an declination of a normal to a characteristic surface is carried out. The equations of bicharacteristics are obtained and three-dimensional fronts magnet-elastic waves is constructed. It is shown, that for the certain values a component of a vector of a magnetic induction, on a surface magnet-elastic quasitransversal waves originate two lacunas. Components of a vector discontinuities are determined.