One of Link's most powerful abilities, often overlooked by new players, is the Sword Beam. When Link has full health (all his heart containers are filled), he can fire a projectile from his sword by pressing the 'A' button. This projectile travels across the screen, dealing damage to enemies from a distance. It's an incredibly useful ability for clearing rooms, damaging tough enemies, and even hitting bosses from a safe range.
To utilize the Sword Beam effectively, always try to keep Link's health at maximum. Collect hearts dropped by enemies, or use Life Potions when necessary. The Sword Beam's power scales with your equipped sword, meaning the Magical Sword's beam is the most potent. Mastering the Sword Beam can make many encounters significantly easier, allowing you to clear rooms without taking damage and conserve your more limited secondary items like Bombs and Arrows.