Is everything energy?

[Lisastronomy]

I wondered about this question. According to me, there 2 ways you can look at it. A system can have energy, or a system is energy. Next to that, the idea of energy, the definition of energy seems a bit vague to me. There are so many types of energy, but what is it really? A system can have energy, like kinetic energy, but aren't in some sense all the particles also energy, and in the end is not everything energy? What are your thoughts on this?

 

[PeroK]

A system can have energy

Correct.

, or a system is energy.

Energy is a quantity associated with a system. Every system has a quantity of energy associated with it, but that doesn't mean that a system is energy. Any more than objects are colour.

Next to that, the idea of energy, the definition of energy seems a bit vague to me. There are so many types of energy, but what is it really? A system can have energy, like kinetic energy, but aren't in some sense all the particles also energy, and in the end is not everything energy? What are your thoughts on this?

You could try reading at least the introduction here:

https://www.feynmanlectures.caltech.edu/I_04.html

Or, slightly more off the wall:

 

[Borek]

What are your thoughts on this?

It is not about what our thoughts are, it is about what is the well established and well tested understanding. There is really no need to break open door.

 

[Rive]

What are your thoughts on this?

It is a bit paradoxical, but the very point of the 'great unifications' is to make an account for all the differences.
The 'everything is energy' is just a thin layer of paint meant to make it look all the same.