The basis of a chemical battery is to have two metals with different electronegativity (willingness to let go of the electrons which form the outer shell of an atom) in contact with each other. This creates movement of electrons from one side to the other which is what electricity is all about. What you can try doing is to insert a piece of copper and a piece of tin in salt water together (or what is often done, stick them in a lemon) and see what kind of voltage you get out of it. You should be able to run a small lamp off of that electricity. Also one weird detail, electricity is only made if there is something that is going to use it. If you put the metal in the lemon nothing happens, but if you connect the metal to a lamp suddenly electricity will be made, start flowing and be used in the lamp! Good luck.