Sweden doesn't lead for quality of music. Norway slays everyone, hands down.
When it comes to the reason for the many metal bands that come out of here, I think it's quite simply what Stilgar said. Scandinavians in general are known for being melancholic, probably due to the long winters and many months of constant darkness. I'd be surprised it that hasn't got something to do with the often very dark/sad music produced in Norway, Sweden and Finland. The Danes are to close to the European continent, and enjoy fantastic beer in abundance, so apparently they are an exception ... = )
Some of you are onto the answer I think ...
One reason for the successful Swedish music scene is surely that there are plenty of possibilities to study music, and to learn how to play instruments from a very young age. Not only metal music, but also world known pop bands (ABBA, Roxette, etc) and producers (Max Martin + many more who produces songs for Madonna and Britney Spears among others). I'm not saying that they write good music, but they cash in some serious money ...
When it comes to the reason for the many metal bands that come out of here, I think it's quite simply what Stilgar said. Scandinavians in general are known for being melancholic, probably due to the long winters and many months of constant darkness. I'd be surprised if that hasn't got something to do with the often very dark/sad music produced in Norway, Sweden and Finland. The Danes are to close to the European continent, and enjoy fantastic beer in abundance, so apparently they are an exception ... = )
It's not just metal... Sweden has been known for its high caliber Jazz musicians for many years (40 or so years???). Many American jazz greats, including Keith Jarrett and possibly Miles Davis have ties with Swedish jazz artists from back in the day.
How about Abba?
There's got to be some sort of historical, cultural reason for the great musicians and great quality of music that comes out of Sweden, though.
Obviously in the states, we have several "scenes" that were/are notorious with certain styles and quality of music.
For a death metal reference, think about Tampa, FL... That was the hot-bed for many legendary dm bands, including Morbid Angel, Obituary, Deicide, Resurrection, Malevolent Creation, Monstrosity, Cynic, Death... Maybe these aren't all from Tampa specifically, but I'm pretty sure they're all originally from FL. Not to mention the legendary Morrisound Studios. For a while there it seemed that every up-and-coming death metal band would got Morrisound to record, and have Dan Seagrave do the album artwork.
These days, it's Andy Sneap for recording and Travis Smith for the artwork. I'm forgetting the name of an important Swedish recording studio... ahem.