Why is electricity not a form of matter?
Electricity is just the flow of current from the charges from the flow of electrons due to positive and negative static charges.
Electricity is not matter because electricity is the movement of matter.
Electricity is the movement of charged particles through a conducting medium.
Usually we think of it as electrons moving through a wire.
However, it is the electrons that are matter, not their movement.
In the same way, wind is the movement of air molecules in a certain direction.
The wind is not matter, but the air molecules are.