Somehow this show has a lot of 'coolness' and I liked it a lot. I am not very sure why it is so cool, but I think first that it has something to do with it's length, I have rarely seen anime that stayed interesting 51 episodes and a movie long. Of course there are side stories, and of course there are dull moments, but somehow most of the episodes actually added something to the show, may it be character development or story development. Isn't that cool? My second coolness-factor for the show is the well-shaped world they live in. Despite it being impossible :P, there are very well though out laws for the alchemy in the world and it's not just presented as magic-that-you-don't-understand-anyway-so-we-won't-bother-explaining- about-it. Then for the third coolness-factor: it's variety, it has humor, story, nice characters, mystery, blood, 'magic', drama, action and least but not last: philosophy. And I must say, it is combined rather well. Even if you don't like blood and action then you might still have this show on your top anime list because of it's story and characters.
Equivalent trade, this is the law that says that to gain something in a process, something else of equal value must be sacrificed. It is basis of using alchemy in the world were Edward en Alphonse Elric live in. Their father went away not long after the brothers where born, so they grew up with only their mother. They knew that their father was an alchemist, so they learned to use alchemy to become just like him. But then their mother died from an illness. They started living with Winry and her grandmother and trained to become better at alchemy. When they found some notes from their father that where left behind, they decided to cross a forbidden line in the alchemy. The notes contained information about the transmutation of living things. They wanted to resurrect their mother with alchemy. But they failed to do so and on top of that, Ed lost his leg and Al his entire body. To save his brothers soul, Ed sacrificed his arm to bind Al's soul to an armor standing around. After Ed's arm and leg were replaced with automail, they set out on a journey to find the philosophers stone. An item that will let you do alchemy without the cost of something of equal value, to get Al's body and Ed's limbs back.