title_body: Is there a difference in quality of using a plastic/wood/metal stirrer?
upvoted_answer: I'm just reasoning...
  
  Polished gold or porcelain must be the ideal stirrers as they won't chemically react. I opt for porcelain as it may also help keeping the coffee warm as its thermal conductivity is less than gold.
  
  Comparing the three you mentioned:
  
  
  Wooden: Sometimes I taste it. So, I don't prefer it that much.
  Plastic: There are many polymers we call plastic in our daily life. Some of these things are really of bad quality and I am suspicious if their thermal resistance is adequate for coffee. I wouldn't prefer them, too.
  Metal: Especially, if you mention polished 18/10 stainless steel cutlery, they probably resist the heat and won't react with anything. So, the only bad thing about them is, they may make your cup colder a bit quicker than usual. Just take the spoon off right after use. This would be my preference.