Abstract <p>Expressions for the magnetorefractive effect and the equatorial Kerr effect of collectivised ferromagnetic metal electrons in the terahertz spectral range are obtained using Maxwell’s equations and the Boltzmann kinetic equation. It is shown that the magnetorefractive effect (the change in the reflection coefficient upon reflection of unpolarized terahertz radiation from the surface of a magnetoresistive metal) is proportional to the magnetoresistance, and the Kerr effect can reach values of the same order of magnitude as for the visible spectral range. The possibility of using these effects is discussed.</p>