- Main article: Story Islands
While Monster Squad does not contain an actual story, the Story Islands are the game's main islands. They require energy to play, and gradually increase in difficulty and reward as the player progresses and unlocks new islands. Many of the game's monsters can be obtained here through random drops.
- Main article: Special Islands
Special Islands are not unlocked by progressing through the game. Some are available all the time, while others are free on certain days and require gems to unlock on other days. Most of the game's material monsters are available here. There are also islands for large experience boosts (but no gold), large gold awards (but no experience), special event islands, single-attribute islands, and several other types.
- Main article: Raid Islands
Raid Islands are a special type of island with different mechanics from the other islands. Only one Raid Island can be unlocked per day, and reset every day. Instead of using a standard team of 4 monsters, the player selects 20 monsters from their inventory when the island is first opened, and those selections are locked for the entire day. Stages must be done sequentially using 5 monsters at a time, with HP losses and monster defeats carrying over from one stage to the next. The raid ends when the player has no monsters left or the final raid boss has been defeated. No experience is given, but gold rewards are typically much higher than other quests, and each raid island has unique monsters that are not available anywhere else in the game.