For example how radio signals of a base transceiver station (BTS) penetrate through buildings?
Radio waves are large wavelength waves, and non metal walls are transparent to the radiation at those wavelengths, depending on the thickness of the walls, because there are no energy level "receptors" to absorb them in bulk by excitation of electronic orbits. The wavelengths start from a centimetre up to kilometre, which is the width of the cycle of the varying electric and magnetic fields.Dissipation happens as the depth/thickness grows, depending on the wavelength because all materials display bulk properties of conductivity at some level.
Metal has organized large distance electronic behaviour and can completely absorb radio waves, again depending on the wavelength and the dimensions .
You can find a related discussion here: Why glass is transparent?