Missile Tanks increase your maximum missile capacity, allowing you to use your powerful secondary weapon more frequently. There are numerous Missile Tanks and Missile+ Tanks (which grant a larger increase) hidden throughout ZDR. These are often found in similar locations to Energy Tanks: behind destructible blocks, in secret rooms, or requiring specific abilities like the Morph Ball, Speed Booster, or Grapple Beam to access. Prioritize collecting these, especially before major boss encounters, as missiles are often key to victory.
