Long Beam
The Long Beam extends the range of Samus's Arm Cannon shots, allowing her to hit enemies from a greater distance. This is a simple but effective upgrade that makes combat safer and more efficient. It is often found early in Brinstar, making it one of the first weapon enhancements you'll acquire.
Ice Beam
The Ice Beam replaces Samus's standard beam with one that freezes enemies solid. Frozen enemies can then be used as temporary platforms to reach higher areas or simply destroyed with a second shot or a missile. This beam is crucial for defeating Metroids in Tourian, as it's the only beam weapon that affects them. It is typically found in Norfair.
Wave Beam
The Wave Beam allows Samus's shots to pass through walls and obstacles, hitting enemies on the other side. This is an incredibly powerful offensive upgrade, enabling you to clear rooms more efficiently and hit enemies that would otherwise be protected. It is usually found in Norfair and can be combined with the Ice Beam for devastating effects.
Screw Attack
The Screw Attack is arguably the most powerful offensive and defensive upgrade. When Samus performs a spinning jump, she becomes invulnerable and damages any enemy she touches. This allows her to tear through most enemies with ease and even destroy certain blocks. It is found in Norfair and makes traversal and combat significantly easier, especially in crowded areas.