If you are an Erasmus student you most probably will be separated from Swedish students - you will leave in detached area full of other Erasmus students (but no Swedes) and will take separate courses.
And as approaching someone and just start talking without any obvious reason is just considered weird, how to meet some Swedish students? There is one proven method - volunteer. That's how Swedes get to know other people - through organized activities. And as this is the most common way of socializing there are a lot of opportunities to do so.
Just contact Student Union or replay to any of ESN advertisement. What you have to do? For example became Erasmus ambassador. And do not be affair of lack of time or hard to fulfill duties - it is more about eating and having fun.
And if helping others, meeting new friends and lot of delicious food still do not convince you: remember that in Sweden word volunteer do not exist and you will be rewarded with a little gift. But what I consider most important is getting to know Swedish members of Student Union which I wouldn't met otherwise and the things about Sweden which I could learn from them.
So if you want to have a full Erasmus + experience volunteering is highly recommended. Help others and have fun - what can be better?