2008 Sienna brakes

When the brakes are applied to my 2008 Sienna, there is a metal grinding noise. Inspected brakes and found that there was abnormal damage/wear to only the outer portion of the front driver brake rotor. There is a lot of material left on the brake pads, approx 5mm. Any ideas? Thanks!

OK, talked to mech, neighbor, he said might be from metal warning tab falling between pad and rotor. Going out to take brake apart right now. Let you know.

Now, there is a loud humming noise when driving. Front wheel bearing!