Tengu format ruling
Rare Metalmorph

Card effect (current official text)Activate this card by targeting 1 Machine-Type monster on the field; it gains 500 ATK. Once, negate a Spell effect that targets that monster. When that monster leaves the field, destroy this card.
Rulings
(1) Select 1 face-up Machine-Type monster. It gains 500 ATK. One time only, negate the effect of a Spell Card that targets that monster. (2) When the selected monster is removed from the field, destroy this card.
- The (1) Continuous-like Effect applies on the field.
- This effect (continuously) targets a face-up Machine-Type monster anywhere on the field.
- If the target is flipped face-down / leaves the field, this card remains face-up meaninglessly.
- If the Machine-Type monster is targeted by either player's Spell Card, that effect is negated when it resolves. A Continuous-like / Lingering Effect that targets a Machine-Type is permanently negated.
- If you chain Rare Metalmorph to Ekibyo Drakmord that targets a Machine-Type monster, Ekibyo Drakmord is equipped but its effect is negated while Rare Metalmorph is active.
- You can activate this card during the Damage Step.
- The (2) Continuous-like Effect applies on the field. This does not start a Chain.
- This effect can be negated by Royal Decree.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Tengu forum — sourced change requests get reviewed.