Is Monsoon legal in Standard, Modern, and Commander?

Monsoon is legal in: Legacy, Vintage, Commander.

Monsoon

Q: What type of card is Monsoon?

Monsoon is an Enchantment. Its oracle text reads: "At the beginning of each player's end step, tap all untapped Islands that player controls and Monsoon deals X damage to the player, where X is the number of Islands tapped this way."

Enchantment

At the beginning of each player's end step, tap all untapped Islands that player controls and Monsoon deals X damage to the player, where X is the number of Islands tapped this way.

Set Ice Age

Rarity Rare

Artist NéNé Thomas