Is Proteus Machine legal in Standard, Modern, and Commander?

Proteus Machine is legal in: Legacy, Vintage, Commander.

What type of card is Proteus Machine?

Proteus Machine is an Artifact Creature — Shapeshifter. Its oracle text reads: "Morph {0} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.) When this creature is turned face up, it becomes the creature type of your choice. (This effect lasts indefinitely.)"