Munich's nocturnal attractions vary with the seasons. The year starts with the abandon of Fasching, the Bavarian carnival time, which begins quietly in mid-November with the crowning of the King and Queen of Fools, expands with fancy-dress balls, and ends with a great street party on Fasching Dienstag (Shrove Tuesday), which can take place between early February and late March. Men should forget wearing neckties on Fasching Dienstag: women posing as witches make a point of cutting them off. From spring until late fall the beer garden dictates the style and pace of Munich's nightlife. When it rains, the indoor beer halls and taverns absorb the thirsty like blotting paper.
The beer gardens and most beer halls close at midnight, but there's no need to go home: some bars and nightclubs are open until 6 AM. A word of caution about bars: most are run honestly, but a few may intentionally overcharge, especially the seedier ones near the main train station. Stick to beer or wine if you can, and pay as you go.
Clubs, discos, and the like can be a bit of a problem in Munich: the bouncers outside are primarily there to add to the often specious exclusivity of the inside. Bouncers are usually rude, crude, and somewhat thick and as such have achieved dubious notoriety throughout Germany. They are in charge of picking who is "in" and who is "out," and there's no use trying to warm up to them.
Munich's growing gay scene stretches between Sendlingertorplatz and Isartorplatz. For an overview check www.munich-cruising.de.