If the same particle, the photon, is responsible for both transporting EM radiation and also carrying magnetic forces, why do magnetic forces travel through opaque objects? Are visibly opaque materials transparent to the magnetic frequency?Is there any material that is opaque to magnetic force, such that placing a flat board of this material reduces the strength of the force between magnets at a fixed distance? Is there any such material that itself is not affected by magnetic forces?
To understand this, you need to learn more physics than you can get from just a few answers here. The photon is responsible for the propagation of an electromagnetic wave. Magnetism is considered to be just the relativistic aspect of a changing electric field. Opaque is not a term relevant to a magnetic field. Permeability and susceptibility are.
