You can do three things with an aspect: invoke for a +2 bonus, invoke for a reroll, invoke for effect.
I think what you are looking for in your case is the third kind. When a character is using his action to start banging on the pan, that creates the aspect "metallic noise" on the scene. Every aspect comes with a free tag, which he immediately uses to invoke for effect (a tag is simply an invoke wihtout the cost of a fate point). Now it is up to the GM to cover the effect. In this case, the "metallic sound" is anathema to the monster, so it makes sense to treat it as a compel on its high concept. Such a compel usually comes out of the GMs stash* of fate points, but since it would go to the monster, and therefore into the GM stash, that is moot. The GM could, however, offer a fate point to a player, if his character would also be affected. A wereform with sensitive ears, for example.
If the monster does not or can not flee, other players could use fate points on the aspect to reflect how the sound is weakening the monster, and grant them a +2 or a reroll on their attacks.
*Usually, the different NPCs don't have individual fate points, but one big pool. This pool is the GMs stash, which he can use to ramp up the power of his NPCs as he sees fit. This is done this way, since NPCs can easily drop below 0 refresh.
I don't know the exact number right know, I think it's something along the lines of the groups combined fate points, or the total spent refresh. But don't quote me on that.