If you summon a Monarch and your opponent uses do still get to use the effect?

You're asking about a scenario in Yu-Gi-Oh! where a Monarch monster is summoned, and your opponent activates a card that would negate its effect. Here's how it works:

It Depends on the Specific Card's Effect

* If the Monarch's effect is continuous: If the Monarch's effect is continuous (meaning it stays active on the field), negating its summon won't stop the continuous effect.

* For example, if you summon "Erebus the Underworld Monarch", its continuous effect to negate the effects of monsters your opponent controls will still be active even if its summon is negated.

* If the Monarch's effect is a triggered effect: If the Monarch's effect is triggered by something happening (like being summoned), negating the summon will prevent the effect from activating.

* For example, if you summon "Caius the Shadow Monarch" and its summon is negated, its triggered effect to destroy a monster on the field won't happen.

Example Scenarios

* Scenario 1: You summon "Erebus the Underworld Monarch". Your opponent activates "Solemn Judgment" to negate the summon. Erebus's continuous effect to negate monsters still remains active.

* Scenario 2: You summon "Caius the Shadow Monarch". Your opponent activates "Solemn Warning" to negate the summon. Caius's triggered effect to destroy a monster doesn't activate because its summon was negated.

Key Point: Pay close attention to the wording of the Monarch's effect. Continuous effects persist even if the monster's summon is negated, while triggered effects are prevented from activating.