punshhh:
You have a misunderstanding as to what energy is. This leads you to ask questions that fundamentally don't make sense. Other posters and I have been trying to correct this. Once you understand what energy is, you will understand why your question doesn't make sense.
Energy is a "phase"/"condition"/"state" of matter.
Wrong.
Energy isn't a phase of matter. It's not a condition of matter. It's not a state of matter. It is a mistake to think of a "kind of thing" called energy. It's a popular mistake, but it is a mistake nonetheless.
This is the way you're thinking about energy, and it's wrong. There are paper airplanes. There is printer paper. There are rolls of parchment paper. All of these things are forms of paper. If we ask what an airplane is made of, it's paper. So, what is paper made of?
This is more how energy works. There are paper dollar bills. There are silver quarters. There are copper pennies. All of these things are forms of money. The dollar bill is made of paper. The quarter is made of a silver alloy. The penny is made of a copper alloy. Money is made of various things.
It's not a chain, as you can see--whereby we say "this dollar bill is made of money--what then is the money made of?" The dollar bill is made of paper, and money can be made of anything.
energy is that force exercised on itself.
No, money doesn't exist by paying itself.
So now I'm just curious if any materialist can tell me what energy is?
What energy is has nothing to do with being a materialist, but you're traveling down a dead end "road" that has already ended--you're currently lost in weeds. Energy is a kind of currency. Energy conservation is a cosmic exchange rate of this currency. There are various forms of coinage, bills, bank accounts, etc; and they all have their own respective constitutions. Perhaps many of them share the same sort. But energy is not a type of constitution for coinage.
Its kind of important because this entire edifice of existence is composed entirely of energy.
To say that something is composed of energy, though, simply means that the thing comes in quantities that you can use to perform work. That is, it means that it's money. It does not tell you what the thing is made of.
If all is energy waves, by what "force" are these waves arranged into the myriad "physical" forms that make up our world?
Strong, electromagnetic, gravitational, and weak. Electromagnetic is responsible for all chemical properties, strong holds atoms and its constituents together, weak plays a role in radioactive elements, and gravity both spawned all of this stuff up and keeps large objects like planets held together.
The answer is not also energy, I hope.
Well, no. Force isn't energy. But hopefully you don't need the lecture on this until you start getting involved in ZPE or something.