Is Necron Overlord legal in Standard, Modern, and Commander?

Necron Overlord is legal in: Legacy, Vintage, Commander.

What type of card is Necron Overlord?

Necron Overlord is an Artifact Creature — Necron Noble. Its oracle text reads: "Relentless March — {X}, {T}, Tap X untapped artifacts you control: Target opponent loses X life. *"This galaxy once knelt before us, and it will do so again."* Power/Toughness: 2/5"