Stereotypical movie zombies are brainless but crave brains to consume. They can only die by destroying their brain. They look like humans but are no longer human but a kind of automatic animal. They are innocent in that it's not their fault they are like this and have no interior malice in their actions.

In a way it's mindless consumption on the capitalist frame (Romeros film in shopping mall helps) but also represent a broken or wrong search for knowledge, or brains or direction, dysfunction.

Generally zombie movies are really about the non zombies, the humans and their dysfunction.