Is Strength of Lunacy legal in Standard, Modern, and Commander?

Strength of Lunacy is legal in: Legacy, Vintage, Commander.

What type of card is Strength of Lunacy?

Strength of Lunacy is an Enchantment — Aura. Its oracle text reads: "Enchant creature Enchanted creature gets +2/+1 and has protection from white. Madness {B} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.) *Don't confuse lunacy with courage.*"