The inherent resistance of the conductor (whatever it is, of whatever material it’s made), will always result in some tiny portion of the signal energy being lost and converted into heat.  When insulation is added, and two or more insulated wires are run together to form a cable, even more changes happen. Capacitance and inductance, varying in proportion with the spacing and configuration of the wires, cause changes in frequency-response and lose important musical information. Phase and transient distortion occur, too, and signal information can actually be lost or false information added through capacitive discharge effects. And unless your cables are either properly shielded or self-shielded by their inherent construction geometry, induced hum and noise can also affect the performance of your system and limit your listening enjoyment.