There is now a large amount of research and proof that everything is energy. Therefore matter is energy.
How anything manifests depends on its vibrational frequency, or, how much energy it contains.
When something moves slowly, that is, in low vibration, it can move so slowly that it appears to be still. Such as a stone or a table. In actual fact the matter of these things is dense. That is all.
On the corollary, if something vibrates quickly, or in high frequency, it can do so much so that it becomes no longer visible to the human eye. That does not mean that there is nothing there. Instead, the vibration is that of a faster or higher frequency.
For example: Thoughts. They don't look like matter, but they matter!
It all begins with our thought.