When a target is killed with any energy weapon, this perk will trigger an explosion centered on the target, similar to a plasma grenade explosion, but smaller. This explosion can cause critical hits and sneak attack criticals, potentially killing nearby targets and propagating further meltdowns.
The explosion projects force, often throwing movable objects, and dismembers corpses. It can also cause friendly fire, damaging the player, companions, and bystanders.
Only direct hits can trigger Meltdown from killing an enemy. If a weapon has a damage-over-time effect (such as the flamer or holorifle), it will not trigger Meltdown if it is the cause of an enemy's death. The "bonus damage" of the pulse gun will also not trigger meltdown.
The damage dealt by Meltdown is relative to the damage dealt by the weapon that killed the target. A powerful weapon such as the Gauss rifle can trigger a high damage meltdown, whereas a flamer's meltdown would be extremely weak by comparison. The meltdown explosion carries any additional effects of the weapon that triggered it, such as igniting enemies, and any critical kill effects. Enemies critical killed by a laser triggered meltdown become ash, while a plasma triggered meltdown produces piles of goo.
- The weapon depicted in the Vault Boy icon is the Plasma Defender.
- Contrary to the in-game loading screen which says the perk affects only laser and plasma weapons, all weapons affected by the Energy Weapons skill trigger the meltdown.
- Weapons which fire in "bursts" in V.A.T.S. can trigger multiple explosions. If an enemy dies before the final shot in a burst, each subsequent hit in that burst will cause another explosion.
- Meltdown explosions will frequently dismember limbs, making this perk desirable when dealing with ghost people.
- Meltdown does not exacerbate the impact power bug of the Gauss rifle or YCS/186 but somewhat remedies it by changing the trajectory of the corpse or causing the impact force of the shot to dissipate when the energy explosion occurs.
- Meltdown does trigger when using Euclid's C-Finder, making it capable of killing enemies it otherwise could not.
- If Meltdown occurs with the Compliance Regulator, it is possible to paralyze the Courier as well.