I know you can shield objects and electronics/electronic signals wires from interference, but that's electromagnetic. I'm talking about a regular neodynium rare earth magnet. Can it be done with a substance, like lead, as opposed to a powered or electrically induced counterforce?
Sure. You can concentrate magnetic flux in a shield of a very high-permittivity material (a so-called mu-metal) and thereby direct most of it around something inside. Alternatively, you can put your object-to-be-shielded inside a superconducting cavity: superconductors oppose the introduction of magnetic fields very efficiently.
Yes, there exist many different types of magnetic shields; they work due to their permeability.
