Flux cannot pass through any medium unimpeded, as certain materials can block or reduce its flow. Magnetic flux, specifically, can be shielded by materials like ultraperm 80 and mu metal, which can reduce its intensity but not completely stop it. Superconductors can entirely block magnetic flux lines, provided the field strength remains within limits. Therefore, the ability of flux to pass through a medium depends on the nature of the flux and the properties of the material. Understanding these interactions is crucial for applications involving magnetic fields and shielding.