Most metallic objects, like aluminum foil, iron or zinc objects, anything with copper or iron oxide paint, steel pots, and iron skillets can block radio waves. However, depending on the frequency of different radio wavelengths, some wavelengths may be powerful enough to surpass certain metals.
Radio waves are a type of electromagnetic radiation that is very useful for communication purposes but not harmful in any way. Radio waves are typically waves with very low frequency and long wavelength. These waves are good for traveling long distances but are not generally very powerful. This allows simple metals to block radio waves.