Is Signature Slam legal in Standard, Modern, and Commander?

Signature Slam is legal in: Modern, Legacy, Vintage, Commander, Historic.

Signature Slam

Q: What type of card is Signature Slam?

Signature Slam is an Instant. Its oracle text reads: "Put a +1/+1 counter on target creature you control, then each modified creature you control deals damage equal to its power to target creature you don't control. (Equipment, Auras you control, and counters are modifications.)"

Instant

Put a +1/+1 counter on target creature you control, then each modified creature you control deals damage equal to its power to target creature you don't control. (Equipment, Auras you control, and counters are modifications.)

Set Modern Horizons 3

Rarity Uncommon

Mana Value 3

Artist Slawomir Maniak

Collector # 168

Scryfall Gatherer