Sir Metal Seal has medium movement speed, but a faster attack rate than Sir Seal, higher attack power (close range and hits multiple cats) and very high health for a Metal enemy (2.75 times that of Super Metal Hippoe). Like all other Metal enemies, Sir Metal Seal only takes 1 damage from all attacks except for Critical Hits.
This is a Metal enemy, so Critical Hitters like Jurassic Cat, Marauder Cat, Space Cat, Waitress Cat or Neneko are mandatory. Unlike most other Metal enemies, who will die rather easily to Critical Hits, this enemy generally requires several Critical Hits to take down. Tesalan Pasalan is a great choice because his Critical Hit can kill Sir Metal Seal in one strike; though be aware his critical hit chance is only 10%, (20% in True Form).