It does. It contains a few rules on combat, including aquatic and aerial. Page 42 is an oft quoted page because it contains a table and guidelines on adjudicating any situation that comes up in combat and setting appropriate DCs and damage values for things like knocking an enemy into a burning brazier or swinging from a chandelier and kicking someone across the room. The DMG also has the rules for skill challenges, traps, hazards, and environmental effects; for handing out balanced treasure, the quest XP system, and a long section with the rules for building NPCs, new monsters and for modifying existing ones, adding templates, etc.