**If you wanna complement around a build of a frontliner with Warcaster and Polearm master**

For example, a tank cleric normally wants to deal damage via Spirit Guardians spell, Paladins would maybe love spirit shroud if you're not an Oath of vengeance with Hunter's Mark and Haste or maybe there are melee Eldritch knights who love to Enlarge themselves. 

To prevent on losing concentration as much as posible as a frontliner and to avoid problems with somatic spells when fighting with sword and board or two weapons (if fighting with two-handed weapons then somatic components may not be a problem for you) you normally want high AC and the Warcaster feat.

If you aim to fish the best damage dealer as I do, then you'll go quarterstaff and board, you'll grab polearm master to combine it with Booming Blade via Warcaster **as a reaction** with a half-elf Oath of Vengeance Paladin to combine it with "Relentless Avenger" or go Eldritch Knight with Crusher feat on top of the other feats and have both builds online at lvl 8 if you're not playing with tasha's extra feat.

This won't work for Paladins who are not Variant Half-elves Moon/Sun elf descent, Rogues, Cleric domains other than the Arcana Domain, Rangers other than Druidic Warriors or Strength based ones.

With "won't work" I mean there's little synergy or you'll need more than 3 feats to make it work, which I don't see as potent for me.