Effect Monsters are Monster Cards with an orange color border. Similar to Normal Monsters, these monsters have an effect, which is demonstrated clearly by the fact that they have the Type 'Effect' beside their regular sub-type (Reptile, Spellcaster, etc.). Effects vary greatly, and are classed in five different types:
Some Fusion, Synchro and Ritual Monsters have effects, and are therefore also treated as Effect Monsters. Toon, Union, Gemini, Spirit Monsters, and some Tuner monsters are all still types of Effect Monsters.
An Effect Monster's effect, if particularly powerful, may be balanced out by the monster itself being weak in ATK and DEF for its level (such as cards like Ancient Gear Engineer or Needle Burrower). Conversely, some cards with ATK that is too high for a monster of its Level may have negative effects detrimental to their use (such as cards like Giant Kozaky or Giant Orc).
Some Effect Monsters have a dot (•) with an effect written after it. This dot usually represents an effect that is active while certain requirements are met, and sometimes this effect can be negated on its own when those requirments are no longer met (ex, the Infernity monsters have effects that are only active while the controller has no cards in their hand, and the Morphtronic monsters have two different effects, and either one of those effects can be active while that monster is in a certain Battle position). Some Effect Monsters that have 2 or more dots usually have effects that give the controller a choice on what they want to do at a certain time (ex, Don Zaloog, or Flying Fortress SKY FIRE), but some of these effects have a basis for the activation (ex, Neo-Spacian Glow Moss and all Fusion Monsters with Neo-Spacian Glow Moss as a Fusion Material Monsters, Gorz the Emissary of Darkness, and Dark Hunter.