Mr. tedibear has to go to Sweden in September. Do you have any recommendations?

My husband is headed to Sweden next month for work, I believe to Stockholm.

He won’t have a lot of time to sightsee, so is there anything that’s he must go to? Also, what food should he be sure to try? He loves fish, and I would guess Sweden is good for that.

Additionally, is there anything he should know about the culture?