If a sword weights more than 3kg(6.6lbs), thats most likely a ceremonial piece than a battlefield iirc. The notion that a sword(as well as plate armor) is heavy to the point of being unwieldy is a popular myth propagated by movies and such. A [url=https://en.wikipedia.org/wiki/Zweih%C3%A4nder]zweihander[/url], a two handed sword, would historically weight about 2-3 kg.
 [url=https://en.wikipedia.org/wiki/Longsword]Longswords[/url] would be 1-2kg. Certainly not unuseable one handed by the average person ^^;

But Ill stop there before I go on full lecture mode lol. I have a tendency to blab on about topics I like. >.>;