Restaurants & Nightlife (Milan)

Hi everybody,
a friend of mine who lives in Bozen is coming to Milan for two days (21th-22th of june) and I was thinking where to take him out by night. I need some suggestions and tips because I don't know any summer event here (some cool places, happy hours and of course disco, especially rock clubs!)

Expats are welcome to join us: my friend speaks German and English and we could organize a gathering all together to show him the international spirit of Milan!

Milla