Is Guardian Shield-Bearer legal in Standard, Modern, and Commander?

Guardian Shield-Bearer is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Pauper.

What type of card is Guardian Shield-Bearer?

Guardian Shield-Bearer is a Creature — Human Soldier. Its oracle text reads: "Megamorph {3}{G} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.) When this creature is turned face up, put a +1/+1 counter on another target creature you control. Power/Toughness: 2/1"