What is "Demus ha'Chayos"?
Radak: It is their appearance, for it already gave the form of their bodies.
Malbim: It is all actions that the Chayos are summonsed to do now. What is totally spiritual, 'Demus' (form) applies only to its actions.
What is the significance of coals of fire?
Malbim: Their action is to burn Beis Hashem and Beis ha'Melech.
Why does it say "k'Mar'e ha'Lapidim"?
Malbim: This is how they will make war (with fire).
What goes among the Chayos?
Rashi: This vision.
Radak: The fire. Malbim - the Chayos themselves are not from the substance of fire, just fire goes among them - "Kach Esh mi'Beinos la'Galgal" (10:6). Fire is attributed to them based on their action.
What is the Chidush that fire has radiance?
Rashi: It is more than [the radiance of] our fire.
Malbim: Nogah illuminates, and does not burn. Hashem showed Yechezkel that His Chesed did not cease. He finished His anger on wood and stones; He will not abandon His nation. He will save them in the end.
What is the significance of lightning coming from fire?
Malbim: It will burn those who destroy His Kadosh city. Sometimes Hashem makes His angels fire, sometimes torches, sometimes lightning? (Yalkut Shimoni Iyov 925).