Is a Pact of the Blade warlock's pact weapon metal?

Question

This came up in our last session. My pact of the blade warlock summoned a longsword to fight a grey ooze. Any nonmagical metal or wood that touches an ooze is corroded. According to the PHB, The pact weapon is magical for the purposes of immunities and damage resistance. So it was unclear to my group whether or not my pact weapon would be corroded when touching the ooze.

The DM ruled that the pact weapon isn't actually metal, but some kind of magical force, so we were ok. But I was interested if anyone else has run into this.

Answer 1

Your DM's ruling is well within the ability description.

From Pact of the Blade

This weapon counts as magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage.

It can be metal, but it could be some other material as the text does not limit/specify the material as metal. Ruling it as a magical force is within the DM's prerogative.

You can choose the form that this melee weapon takes each time you create it.

(Reference is SRD p. 47/PHB p. 107-108)