Bloon Melter is an Advanced Powercard in Bloons Card Storm, introduced in version 2.0. It destroys a target Bloon on the player's side and does 20 damage to the opponent. It will trigger any On Popped or On Destroyed effects on the target.
The main purpose of Bloon Melter is to destroy friendly bloon(s) in favor of the player. The face damage is terrible and almost never matters, unless the opponent is critically low on health.
The player can use Bloon Melter to deactivate an opponent's Corvus Academy of Arts without using a Monkey removal.
If you are going to use it to damage the hero however, use it on bloons that are weak from the start or too weak to fight the opponent such as Swarm Red Bloon.
Bloon Melter can synergize with Bloons with an "on destroyed" or "on popped" keyword such as The Eternal, Volatile Bloon, or Black Bloon. The Eternal or Volatile Bloon have powerful effects that can justify Bloon Melter in a deck, and the former is usually the main incentive for this card.
Eternal decks may rely on Bloon Melter to keep building its HP and re-playing the stronger Eternal, plus more Bloontonium.
Black Bloons give a card right away upon popping, which may be helpful if desperate for more card draws.
You can also place these bloons listed with Volatile Bloon to activate all abilities if you like.
Bloon Melter can also be used for removing bloons for Hastening Bloon consistency, although doing so is expensive and may not warrant the deck slot.