And yes, if I can taste metal in my vape, metal ions are actually in the vapor, or transporting through (heaven forbid) the drip tip. The human tongue cannot taste metal where it is not present. I taste metal all the time in really bad or too-high-powered coils.
Well, I do know that metal ions are known to bind with protein, but I'm not sure if there is any protein in vaping liquid.
On a lighter note, a metallic taste in the mouth is a common complaint and can be due to a variety of causes - from medication you may be taking to dental problems. Are you on any medications? How are your teeth? Do you have a purdy mouth? In the absence of other symptoms, it is unlikely that a metallic taste in your mouth indicates serious disease. But if you haven't had a thorough general checkup recently, I would suggest seeing your doctor to rule out any undiagnosed health problems. Some people report tasting metal right before a seizure, so it's no wonder so many people are concerned about their metal taste. If you're worried, or think you might have a seizure disorder, contact a doctor.
Anxiety does appear to cause a metallic taste in people's mouths. What's interesting, however, is that there doesn't appear to be a medical reason for it. Even during the fight or flight response, there isn't necessarily anything activated in the taste buds that should be creating this metallic taste. There are a lot of different theories for why someone would experience a metallic taste, and all of them appear to be true for different people. These reasons include:
Bleeding Gums Stress can cause a reaction from bacteria inside of your mouth that make your gums bleed. Blood happens to tastes like metal, and can be tasted even if the amount of blood is barely perceptible. It's possible that during anxiety attacks and stress, you're experiencing a minor gum bleed.
Over Sensitivity to Taste During periods of anxiety, it's not uncommon to be more sensitive to your usual tastes than others. In addition, there is some scientific evidence that during periods of intense stress, your taste buds may actually change, so the same taste may have a different affect.
Stomach Acid Those with gastroesophageal reflux disease, or other related acid reflux problems, may taste metal when the acids reach the tongue. During times of intense stress and anxiety, stomach acid may be more likely to come up.
Medications Medications that are used to treat mental illness may also cause this metallic taste.