Is Midsummer Revel legal in Standard, Modern, and Commander?

Midsummer Revel is legal in: Legacy, Vintage, Commander.

What type of card is Midsummer Revel?

Midsummer Revel is an Enchantment. Its oracle text reads: "At the beginning of your upkeep, you may put a verse counter on this enchantment. {G}, Sacrifice this enchantment: Create X 3/3 green Beast creature tokens, where X is the number of verse counters on this enchantment."