Rambam: Yesodei HaTorah 2:3

by Rabbi David

Laws of the Foundations of the Torah... All plagiarized from the Rambam

Law 3: There are three types of creations. Vegans are not one of them.

Three categories of creatures Gd created in His world. There are probably more, but they're not creatures. They're probably basilisks, minotaurs, centaurs and other taurs. Gd didn't create those. If it's in Dungeons and Dragons, that doesn't mean Gd created the creature. There might be a fourth Dungeons and Dragons category, but the Rambam was not privy in 12th century Cordoba. Though he was hip and sported the turban.

First: Those that have matter and form like humans, animals, plants, metals. Bodies. We're talking about bodies here. Even unattractive creatures. Gd creates those too.
They come into existence and cease. All of this physical matter stuff will end. Even if you freeze your body, the ice will melt at some point. Then you're gone. Transmutating into a metal doesn't work. I understand many people have thought about it. It won't work. You may get a couple hundred years out of that. That's about it. 
If you marry somebody not attractive, it won't last forever. I hope that brings you comfort and inspiration.

Second: Those of matter and form that don't change. Like the spheres and stars.
I have no idea what spheres are. Circles. I guess. Stuff made in art class with a compass, they don't change. Unless if you have a shaky hand. If you place that sharp pointer thing in the correct place and hold it down strong, it doesn't change. Those circles and stars don't change.
The first category is different as it ceases and changes. Wrinkles. The Rambam is teaching us about wrinkles. Wrinkles and dry skin are the difference. The second category doesn't have to use lotion with aloe.

Third: Those with no matter at all. They just have form. We're talking about angels. Shapes with no matter. But they do matter. They matter with no matter. Angels can get down on themselves. That's why you should always tell them they matter.
Their forms differ. And they weigh nothing. One guy is a human and the other an octagon. We don't judge angels.
They take up no space. Probably always thin. Never have to diet. They never talk about how fat they get over a Three Day Rosh Hashana. They never complain about getting bloated from Challah. They never have to wait in lines. They never get caught sneaking into movies. They probably just sneak onto buses and take seats. You see a guy sitting in the aisle seat with an empty spot by the window, it's probably one of these guys sitting there.
Some of them might be minotaurs. Weightless minotaurs. I can't promise. I'm just conjecturing.

Everything has form. And we're going to die. That's the point the Rambam is teaching us in this Halacha. We're going to die. I hope that helps you understand angels.