Radios use electromagnetic fields. The EM field can induce a current in an antenna. This current is what is received and amplified. Recall that an antenna, at

Radios use electromagnetic fields. The EM field can induce a current in an antenna. This current is what is received and amplified. Recall that an antenna, at its simplest, is just a length of wire. Keep in mind that when you are working with antennas, you have to forget about Kirchoff's laws, because the simplifying assumptions that make Kirchoff's laws work aren't true for antennas. By Kirchoff's laws, you can't have current flowing through a wire that isn't connected to anything. However, the charge density of the wire is changing under the influence of the radio waves--the radio waves are pushing the charges in the wire from one side to the other, and then back again.