Transferring Current Through A Substrate

I had a thought and was curious if it possible. I would imagine that someone has thought of this or tried it before. Please forgive me if
this is deemed ludicrous as my electrical knowledge is somewhat limited.
Given a low voltage high amperage DC power source would it be possible to transfer power through a single medium to a load (e.g. contiguous piece of metal) by modifying in some effect either the positive or negative signal?
I would say that for safety purposes the positive side should be the signal that is modified. As I imagine it, the load would need a way to extract or interpret the power from the medium either as a modular add- on or as a built-in capability.
Would a technique such as frequency division be applicable?
Would there be a possibility that when a high load device is attached, other low load devices are deprived of current? Then as a possible solution to this, would it be possible or advisable to create various channels that carry a different amount of current (assuming something like frequency division is possible) and associated modules to extract this signal from the conductor?
What affect might this have to the substrate? My thought is that the conductor would increase in temperature.
Thank you for your consideration of this.
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