As the title suggests, if one holds a touch attack spell (i.e. shocking grasp) and is attacked by a swarm.
Does the swarm's attack release the held touch spell and receive damage, or does it release the spell with no damage?
As RAW goes, swarms are immune to or take half damage from certain attack groups. In the text it says they are immune to spells that target a specific number of creatures (or single target spells).
Breakdown:
Magius Magus: Cast Shocking Grasp, holds charge
Swarms McKinnon (bat swarm): attacks Magius
???
Profit
No. A held charge does not discharge unless you touch something, as opposed to the other way around. Otherwise the held charge would go off because you are wearing clothes. Note that if you reach down to your belt and open up your belt pouch you touched it and discharge the spell on your belt pouch. If someone throws their belt pouch at you though and it hits you in the arm, face, or elsewhere, you didn't touch it - it touched you.
Granted that is a very subtle difference, but held charge completely breaks down if that difference doesn't exist.
Without it:
Monster bites you, and gets a mouth full of shocking grasp.
Archer shoots you, and the shocking grasp discharges on the arrow sticking out of your chest.
Barbarian cleaves you in two with his greataxe and the shocking grasp discharges on his axe.
Thanks for the quick replies.