For Druid Wild Shape:

> 
> PRIMAL STRIKE Starting at 6th level, your attacks in beast form count
>  as magical for the purpose of overcoming resistance and immunity to
>  nonmagical attacks and damage.
> 
> 
> 

For the Monk:

> 
> KI-EMPOWERED STRIKES Starting at 6th leveI, your unarmed strikes count
>  as magical for the purpose of overcoming resistance and immunity to
>  nonmagical attacks and damage.
> 
> 
> 

The text seems to indicate the ability to bypass magical immunity requires a *feature*.

Alternatively, I have read that natural attacks and unarmed attacks aren't "weapons," and therefore you should just be able to pummel the Werewolf with your hands if your sword fails:

> 
> Melee Attacks (PHB p.195 (or in errata), emphasis mine). The rule on unarmed strikes should read as
>  follows: “Instead of using a weapon to make a melee weapon attack, you
>  can use an unarmed strike: a punch, kick, head-butt, or similar
>  forceful blow (**none of which count as weapons**). 
> 
> 
> 

However the errata for Monster Manual I guess clears that loophole:

> 
> Global Damage Resistances/Immunities. Throughout the book, instances
>  of “nonmagical weapons” in Damage Resistances/Immunities entries have
>  been replaced with “nonmagical attacks.”
> 
> 
> 

We temporarily *ad hoc*'d an answer in our game to say the Stirges summoned by the druid were magical creatures(Fey) and hence had magical attacks against the Werewolves, even though they were 1HD(d4). Now I see the druid made the Fey part up, and they are beasts, but oh well.

What is the real rule here?