As with all the Vasebreaker levels, try to break the vases on the right side of the lawn first. The most dangerous zombies in this level are the Football Zombie and the Jack-in-the-Box Zombie (both of which have a weakness to Magnet-shroom, emphasizing its importance).
Plant Magnet-shrooms in the front of the lawn and protect them with Pumpkins as soon as possible when you get them.
Place Hypno-shrooms on the left side, in case a Football Zombie gets away. There is no time limit, and you can let out the zombies whenever you choose to. Therefore, a viable, but slow strategy is to wait until Magnet-shrooms recharge before breaking certain vases.
The level's name is a reference to the mnemonic "[letter] is for [word that starts with the same letter]." It says metal because most of the zombies have metallic objects on themselves that be stolen by a Magnet-shroom.
In this level, it may be possible for Jack-in-the-Box Zombie to get into the house without its Jack-in-the-Box if there is a Magnet-shroom next to it, as it will steal its Jack-in-the-Box, allowing it to walk freely.
This is also the only Vasebreaker level where the player can avoid having its Jack-in-the-Box explode, although it is possible to kill it with a perfectly timed Squash or other instant-kill plants.