When is a spell "on" a target for the purposes of Dispel Magic?

Question

Suppose my character is currently under the effects of the Heat Metal spell (targeting his breastplate) and is also caught by the Entangle spell (i.e., I was in the Entangle area of effect when it was cast during the last round, and I failed my saving throw). Finally, my character is cursed by the Bane spell. On my turn, I cast Dispel Magic on myself. What happens?

As I see it, these are all cases that aren't very clearly answered by the relevant text of Dispel Magic. They're similar, but ultimately, I believe there are three separate sub-questions here:

1. When I target myself with Dispel Magic, does it remove the effect of Heat Metal on my breastplate (is Heat Metal spell "on" me or "on" the breastplate for the purposes of Dispel Magic)? My intuition is that (RAW) the caster must target the breastplate.
2. Does Dispel Magic remove the effect of Entangle, given that it's an area-of-effect spell that is affecting me, not a spell specifically targeting me. The relevant text of Dispel Magic states, "Any spell of 3rd level or lower on the target ends." Is the Entangle spell "on" me? If so, does the entire Entangle spell end, or do I just get disentangled? Does this extend to other area-of-effect spells? In this case, my intuition is that (RAW) the caster must target the area-of-effect, not themself, and that targeting themself does nothing to the Entangle spell or the restrained effect.
3. What happens to the Bane spell effecting me? Does it dispel the Bane effect on me alone or does it dispel the Bane spell altogether (thus freeing anyone else also cursed by the same casting)? Or do I need to target the Bane spell in this case also? Here, my intuition is that casting Dispel Magic on myself (RAW) unwinds the Bane spell altogether, so all players affected by Bane would have it removed after I cast Dispel Magic on myself.

Here's the tricky part: assuming that the answer to question 2 is "you must cast Dispel Magic on the Entangle effect, not yourself, in order to end it," but the answer to question 3 is "Casting Dispel Magic on yourself ends Bane altogether," then why are these different? The only material differences seem to be that Bane targets multiple creatures at casting instead of creating an area-of-effect, and Dispel Magic says nothing that explicitly differentiates these cases. The difference appears to come down to whether an area-of-effect spell or a spell like Bane is "on" me when it effects me. What is the rule here and what about a spell's description tells me which of these cases applies? (Assuming my intuition above is correct).

These questions get at the interpretation of Dispel Magic and are very relevant, but do not clearly answer these questions.

• What happens when you target a "magical effect" with Dispel Magic?
• When can a magical effect be targeted with the dispel magic spell?
• Dispel Magic: What is the difference between a Creature under the effects of a spell vs a Magical Effect?

Notably, the accepted answer on the second question above is "Ask your DM," which I'm starting to think is the correct answer for all Dispel Magic questions. 😅

Answer 1

Your intuition is pretty good here. Spells are only "on you" if the spell was actually cast on you personally. However, in the case of spells that target multiple people, dispel magic only ends the part of a spell that's on you personally.

To address that last point first, we have an official answer to lean on. Question 183 in the Sage Advice Compendium gives us:

If dispel magic targets the magical effect from bless cast by a cleric, does it remove the effect on all the targets?
Dispel magic ends a spell on one target. It doesn’t end the same spell on other targets.

Since bane works exactly the same way as bless, we have our answer to that part.

Heat metal specifically targets a metal object, and that can then burn the person in contact with it. Since the metal object is the thing that the spell is actually on, you'd need to dispel the armor specifically, not the person wearing it.

And finally, entangle is as you said; the spell is on the area, not you personally. You'd need to dispel the "magical effect within range", not the person being restrained by the plants animated by the magical effect.