Actually, that is true. Electricity, light, heat, matter and sound are all forms of energy. They are transformations of the same substance.
I recall my old physics lessons now at school where we had to label what the energy had transformed into. An object falling from a height would have gravitational potential energy, when falling it would have kinetic energy, when hitting the ground it would have sound energy.
Einstein took this thermodynamics 101 one level higher. He equated matter and energy with his famous E=MC^2. This equation basically says that matter becomes energy at the speed of light. But it also says something else, that whenever an object moves, a fraction of the momentum energy it gains is converted into mass. At small speeds, this is neglible, but at high speeds like approaching the speed of light, the effects are substantial. These are known as relativistic speeds. At the speed of light a mass will becomes infinite. This means it will require infinite energy to travel at the speed of light.
So matter, electricity, heat, sound, light are all transformations of the same substance.
It’s a bit of a cliche to say, “It’s all energy” I hear that one a lot. It is not energy that this ultimate substance is, in fact whatever it is, we know it is definitely not a material. That we know for a fact. It is the different modifications of that immaterial ultimate substance which give rise to all those diverse forms.