Spin angular momentum can be transferred across magnet/metal interfaces in the form of a spin current. In magnet/metal heterostructures based on insulating magnetic materials, the spin current flow across the interface gives rise to the so-called spin Hall magnetoresistance. The aim of this PhD thesis is to explore spin current flow in magnet/metal heterostructures. In a first step, different insulating magnets (magnetic oxides as well as Heusler compounds) in combination with Pt shall be studied. Subsequently, Pt shall be exchanged against a metal with non-trivial toplogical properties, such as a Weyl semi-metal, or metals featuring antiferromagnetic order.