Melee Magic doesn't reinvent the wheel, it plays just like Commander but without the baggage. Here's how it differs:
Melee Magic card pool primarily uses In Universe standard legal sets starting from Throne of Eldraine onward (some exceptions apply, the full list can be found here.)
NO reprints from older sets are legal, only NEW cards introduced in most standard legal sets. (example Demonic Tutor from Strixhaven Mystical Archives not legal but Vaultborn Tyrant from Outlaws of Thunder Junction The Big Score is legal.)
To keep power creep to a minimum, no supplemental products such as Master Sets, Commander Pre-Cons or Jumpstart cards are legal in Melee Magic.
Additionally:
You Commander can be any Legal Legendary Creature, Planeswalker, Vehicle, Spacecraft, Saga, Battle or Artifact with a Legendary Creature on the back. Initial cast from your Command Zone must following timing rules and restrictions. Subsequent cast from the Command Zone (Commander Tax) is 1 Generic Mana more per cast.
The Ikoria Companion mechanic as initially released is supported, it doesn't count toward the 99 card count, starts in the command zone. All color identity and companion specific rules must be met.
No Ban list as this format pre-emptively avoids the Commander extensive card pool. As the card pool expands, considerations will be made to keep the format healthy.