Games like Send More Monsters
Games like Send More Monsters include Kingdom Rush Frontiers - Tower Defense, GemCraft - Chasing Shadows, Bloons TD 6, Kingdom Rush 5: Alliance TD, and Sir, We Have an Orc Problem. We matched them by the tags players give Send More Monsters on Steam (Strategy, Tower Defense, Incremental, Wargame, and 2D): closest matches first, and among equally close ones the better-known games.

Kingdom Rush Frontiers - Tower Defense
Shared: Strategy · Tower Defense · 2D

GemCraft - Chasing Shadows
Shared: Strategy · Tower Defense · Top-Down

Bloons TD 6
Shared: Strategy · Tower Defense · Multiplayer

Kingdom Rush 5: Alliance TD
Shared: Strategy · Tower Defense · 2D

Sir, We Have an Orc Problem
Shared: Tower Defense · Incremental · Strategy

Kingdom Rush - Tower Defense
Shared: Strategy · Tower Defense · 2D

Foxhole
Shared: Wargame · Strategy · Top-Down

Legion TD 2 - Multiplayer Tower Defense
Shared: Tower Defense · Strategy · PvP

Total War: WARHAMMER II
Shared: Strategy · Fantasy · War

Plants vs. Zombies GOTY Edition
Shared: Tower Defense · Strategy · 2D

Minimalist Tower Defense
Shared: Strategy · Tower Defense · 2D

Tower Wizard
Shared: Incremental · Strategy · 2D

Dungeon Warfare
Shared: Strategy · Tower Defense · 2D

Idle Champions of the Forgotten Realms
Shared: Strategy · Incremental · Fantasy

Kingdom Rush 6: Genesis TD
Shared: Strategy · Tower Defense · 2D

Mindustry
Shared: Tower Defense · Strategy · Base Building

Orcs Must Die!
Shared: Tower Defense · Strategy · Fantasy

Kingdom Two Crowns
Shared: Tower Defense · Strategy · Fantasy

Kingdom Rush Origins - Tower Defense
Shared: Strategy · Tower Defense · 2D

GemCraft - Frostborn Wrath
Shared: Tower Defense · Strategy · 2D

Totally Accurate Battle Simulator
Shared: Strategy · War · Indie

Creeper World 3: Arc Eternal
Shared: Strategy · Tower Defense · Indie

Company of Heroes 3
Shared: Strategy · Wargame · Singleplayer

Warstone TD
Shared: Strategy · Tower Defense · Fantasy