Small amount of rare-earth elements may have negative effects on the formation of some metallic glass alloys. The rare-earth elements may react with some atoms of the alloys to form compounds of high melting points or be absorbed on the surfaces of the heterogeneous catalysts in the alloys to activate the heterogeneous nucleation. In this case, the rare-earth elements have no effects on enhancing the stability of the metallic glass phase but enhance the heterogeneous nucleation and decrease the metallic glass forming ability and thermostability.