Is Singer of Swift Rivers legal in Standard, Modern, and Commander?

Singer of Swift Rivers is legal in: Legacy, Vintage, Commander.

Singer of Swift Rivers

Q: What type of card is Singer of Swift Rivers?

Singer of Swift Rivers is a Creature — Merfolk Shaman. Its oracle text reads: "Flash When this creature enters, put a shield counter on another target creature you control. (If it would be dealt damage or destroyed, remove a shield counter from it instead.) You may cast Merfolk spells as though they had flash."

Creature — Merfolk Shaman

Flash

When this creature enters, put a shield counter on another target creature you control. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)

You may cast Merfolk spells as though they had flash.

Set The Lost Caverns of Ixalan Commander

Rarity Rare

Mana Value 3

Artist Gabor Szikszai

Collector # 98

Scryfall Gatherer