Glad you asked that! Lots of people have seen enough Hollywood vampire movies to know what Hollywood thinks. That, however, is not always in keeping with the mythology of the vampire.
I think there are very few people that have not seen a vampire movie in which the vampire is destroyed by a stake through the heart. There are lots of other methods in the mythologies of various cultures around the world, but Hollywood really likes the stake. Sometimes the ‘brides’ of the vampire are staked in their coffins, but more often than not, the main vampire in the movie gets staked through the heart in some dramatic fight scene. If you’re a Buffy fan, they’re nearly always staked in the fight scene and not necessarily through the heart.
The question is, where did that idea come from? Hollywood seized on the myth of the wooden stake for the dramatic and horrific effect, particularly in the much tamer 1920 through 1960′s era vampire movies. Originally, the stake’s material was not such an issue. The purpose of the stake was to keep the deceased in the coffin. They were not actually staked until the box was in the grave itself. The stake was supposed to be long enough to go through the box and into the earth, keeping the body attached to the grave. Whether the stake itself was wooden or metal, such as iron, was alot more dependent on local beliefs and materials available rather than there being a single idea of how to keep a vampire in the grave.
Now that you know what the stake was supposed to do, the next question invariably is why the heart. There’s a couple of different mythological reasons on that too. Some believed that they actually had to have several stakes driven in at various points in the body so the vampire couldn’t just sit up and raise themselves off of a stake. Some cultures believed that putting it through the chest did a better job of holding the body to the coffin rather than just putting it through soft tissues. Other cultures believed that your soul resided in the area of your body associated with your heart. If the soul couldn’t rise up to wander the earth, the body couldn’t either.
Kind of makes you grateful for mortuary science doesn’t it.