I've been wondering for a while about this, but there's no universally accepted checklist that defines whether a game is Metroid-like or Metroidvania. In common usage, a 2D side-scrolling game with an interconnected maps rather than discrete stages is often classified as a Metroidvania.

However, I think these two genres can be distinctly defined, and I think this is a good definition.

The Broadest Interpretation

A broad interpretation would be using the origin of the genre name:

• Metroid-like is a game with similar design principles established by Metroid.
• Metroidvania is a game with similar design principles established by Castlevania: Symphony of the Night. In software engineering terms, Metroidvania extends Metroid-like.

That distinction alone is insufficient to create a detailed distinction, but I realize that the key difference is progression. With that knowledge in hand, let's draw a common trait and distinct trait between Metroid-like and Metroidvania,

The Traits

Both Metroid-like and Metroidvania share several common traits:

• 2D side-scrolling: Reaching zone in higher heights is a staple to both
• Interconnected maps: A large, usually themed area that is connected to another large themed area
• Exploration gated by acquiring something: a path to a certain area is blocked until player has acquired power-up somewhere in the explorable areas
• Save room: Save room replenishes player health, devoid of danger, and saves the game's progress proper, not a temporary save

The Distinction: Progression

Trait	Metroid-like	Metroidvania
Exploration progression	Can be non-linear, backtracking may be optional or restricted	Nonlinear; backtracking is an integral part of progression
Character progression	By only acquiring power-up	By both acquiring power-up and leveling up
Character progression gate	Power-up gated by exploration	Leveling up is not gated. Tedious, but not gated
Progression against hard enemy	Dexterity required because characters have soft power ceiling limited by exploration	Leveling up will substantially reduce the executional difficulty of otherwise challenging encounters

About Overleveling

One trait of Metroidvania is: Players can overcome hard enemies by overleveling IFF overleveling can meaningfully substitute for dexterity. The IFF condition means "if and only if", i.e. if and only if character progression permits sufficiently large, repeatable increases in combat effectiveness such that an otherwise hard enemy can be overcome primarily by increasing character level/statistical power.

This criterion excludes games where leveling provides numerical growth but cannot meaningfully substitute for player skill, as is often the case with Souls-like progression. The distinction is between:

Player skill + finite character progression.

And not:

Character progression can substitute for player skill.

A Metroidvania has to provide a statistical escape route around the skill gate.

Full Definition

So the full definition list can be constructed as follows:

Metroid-like

1. 2D side-scrolling
2. Interconnected world
3. Exploration gated by acquiring something
4. Save rooms
5. Character progression primarily through finite, exploration-dependent power-ups
6. Power-ups themselves are gated by exploration
7. Character power has a soft ceiling determined by exploration
8. Dexterity remains necessary for sufficiently difficult encounters

In short, Metroid-like is:

Exploration ➡️ power ➡️ new exploration

Metroidvania

1. 2D side-scrolling
2. Interconnected world
3. Exploration gated by acquiring something
4. Save rooms
5. Character progression includes repeatable/accumulative numerical progression
6. Numerical progression can be increased independently of discovering new traversal abilities
7. Overleveling can meaningfully compensate for player skill
8. Sufficiently difficult enemies can be defeated through character power rather than exclusively improved execution

In short, Metroidvania is:

Exploration ➡️ resources ➡️ character power

Apply Traits to Games

Now with the definition out, we can apply to existing games:

Game	Progression model	Genre
Metroid Prime	Find power-ups through exploration only, but is a first-person shooter	Not Metroid-like
Super Metroid	Find power-ups through exploration only	Metroid-like
Metroid Dread	Find power-ups through exploration only	Metroid-like
Hollow Knight	Find power-ups through exploration only. Despite nail upgrades, charms, masks, no conventional leveling is present.	Metroid-like
Castlevania: Lament of Innocence	Has whip power ups, equipments, but no leveling and, is a 3rd person 3D action	Not Metroid or Metroidvania
Castlevania: Aria of Sorrow	Leveling is a meaningful upgrade method.	Metroidvania
Castlevania: Symphony of the Night	Leveling is a meaningful upgrade method.	Metroidvania
Castlevania: Symphony of the Night, Richter Mode	No leveling, power-ups through exploration only	Metroid-like
Bloodstained: Ritual of the Night	Leveling is a meaningful upgrade method.	Metroidvania

Voila! Two distinct genre that has clear definition!

The Case of Carrion

The indie game Carrion is a unique specimen (ha!). Carrion lacks power to become a statistical abomination, thus disqualifies it as Metroidvania; and while backtrack are limited and requires power up to explore further, each power up requires player to detach biomass and control the detached biomass, thus becomes much weaker. Otherwise, it fully match the traits of Metroid-like.

But seriously? A game where progression is a downgrade? Is this the Anti-Metroid? Imagine Samus finding the Varia Suit, then its description is:

Congratulations! You can now survive extreme temperatures. Unfortunately, your arm cannon is unusable because it has gaps that can compromise the suit.

Wait, isn't that pretty close to Metroid Dread... Ugh. I am not replaying that game.