My last two IPAs have had a distinctive metallic taste...or it could be I just over battered.
Over battered? What does that mean? And how sure are you that it is metallic and not something else? Is the flavor similar to putting a penny in your mouth? Or similar to blood?
In any case, I'm trying to learn what causes a metallic taste in home brews related to the process. The water I use is very good, soft and near neutral pH...and all my malty styles never have a hint of this taste.
Typically, we would look at water chemistry first. Higher concentrations of copper, manganese, zinc, or iron could cause obvious metallic tastes. These could come from the water itself or from using these reactive materials within your brewing process. But then you say that it only happens in you hoppy beers, which may make that point invalid.
Next up would be oxidation of lipids, which may
cause metallic flavors like Denny said, but the science behind that isn't well understood yet. That's not to say it isn't true, it's just that the explanation hasn't caught up with us yet. Something interesting here is that removing spent hops & hot break from your kettle efficiently can ensure a lower level of lipids in the fermenter (Source: Journal of the Institute of Brewing, Sept/Oct 1985 - http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1985.tb04349.x/pdf
Perhaps in your hoppier beers you are not removing enough of the hop mass before the fermenter or are not getting enough hot break (combined with your water) to get below your personal taste threshold for this metallic taste.