Brussels is not only the capital of Belgium, a small country in Western Europe, but it also functions as the capital of the European Union, since that is where most of the union's administrative buildings are placed. However, you can't just walk into a pub and ask for a beer in Belgium - the folk there take pride in having hundreds of different types of beers to choose from.
No other country in the world produces as wide of a variety of beers as Belgium, which means that you should take your time to talk with people or study on the internet the types of beers you would like to try out during your visit. Another word of advice is to keep in mind that most of the Belgium-native beers are stronger and higher in their alcoholic content than their counterparts in other countries.