Duelingbook Forum

If I were to use a card like Metal Reflect Slime and my opponent plays Book of Moon on it after it becomes a monster, will it just be a monster in facedown defense position, or will it be a set trap card?

If a Trap Monster is flipped face-down by Book of Moon or the likes, it will be Set as a Trap card (return it to the same position it was activated). You can activate it again the next turn,

However, with the new rulings where they no longer take up a s/t zone while being a monster, if your s/t zones are full when book of moon resolves, the card is instead sent to the graveyard by game mechanic

@Chaseer

If the Trap Monster via effect is not treated as a Trap anymore, then it will remain in the monster zone flipped down.

@Shugunou

Metal reflect slime while it his a monster it no longer occupied the spell and trap card zone, but it his still treated as both a trap, and a monster, so if you book of moon metal reflect slime it will return to the controller empty spell and trap card zone if their his one, if they are no space available, then it his destroyed while book of moon resolve. @Unorthodoxical-Princ was thinking about the Paleozoic, does are trap card that activated in the graveyard to be special summoned as monster, and does one are only treated as monster when they are special summoned

Because metal reflect slime is still considered a trap card, it will be reset to the zone that it was activated in. If there are no zones available for it to be set into then instead slime will go the gy.