Me and a couple friends are confused as to when your opponent can respond with their quick effect monster effect. For example, I normal summon a monster and proceed to link off with it. Then my opponent tried to chain their monster, “Unchained Soul of Rage” to the link summon. I state that my link summon does not start a chain and they therefore cannot attempt to activate their card effect. Then they said that they are not chaining to the summon, they are activating their affect after I summon. But I told them they aren’t allowed to activate their affect cause I am the turn player and I have priority and they can only respond to effects that start a chain or something that meets the activation/trigger requirements. What I am basically asking is when can your opponent use quick effects during your turn, specifically main phase? During your main phase, your opponent cannot activate anything they want, even if it is a quick effect, unless they are responding to a chain or their card has a trigger effect correct (of course they can activate whatever they want when I end my main phase because I am passing priority to them)?