What are power lines made of?

Answer 1

Atoms.
Electricity is not something you can "break down" into "elements".

You can use electric energy to drive certain chemical reactions. For example, you can split water into hydrogen and oxygen. But that does not mean that electricity is "made of" hydrogen and oxygen. Water is.

Electric current is made of electrons flowing in a conductor such as copper or aluminum. (e.g. wire)

The wire does not weigh any more, or less, for having electricity flowing in it, as the electrons in question were and are always there, even if no electricity is flowing. It is just that in conductive materials (like most metals, like copper) the outer electrons of the atoms are fairly loosely bound to the nuclei. So electric current involves shoving electrons into one end of the wire and taking the same number out the other end. This is done by applying "electromotive force", EMF, which we measure in volts and is commonly called "voltage". The total number of electrons in the wire remains the same. The electrons just move along from one atom to the next, so the net charge in the wire remains zero.

This does make electricity "weightless", I suppose. However this would not cause the wires in transmission lines to "hang upwards" because the weight of the wires themselves would still be there. Again, the wires don't weigh any more - or any less - for having electric current flowing in them.

You can transport by train chemicals and materials which, when arranged in the proper way, produce an electromotive force. We call such an arrangement a "battery." However batteries are a very inefficient means of storing electrical energy. Just for comparison, a liter of gasoline contains the equivalent of 9000 watt-hours of energy; a liter's worth of lithium-ion battery, the best currently available, contains only 250 watt hours.

The materials from which primary batteries (those that start out charged and can only be used once) are not in infinite supply, either, so the idea of just making batteries instead of using fossil fuels won't work. There's a LOT more latent energy in the ground in the form of fossil fuels than there is in chemicals that could make batteries. And batteries aren't the most environmentally-friendly things either.

Electricity flowing in wires is an extremely efficient, clean, safe, and convenient way to move energy around. So much so that if you have electricity, about the last thing you want to do with it (from an energy efficiency point of view) is to use it to e.g. make hydrogen or charge a battery.
moving electrons

Answer 2

A generator manufactures electricity. In a generator, something causes the shaft and armature to spin. An electric current is generated

Answer 3

A composition of aluminum conductors wrapped around a steel messenger core. The steel core is used to support the weight of the wire between the long spans from tower to tower.