Metro has emailed me their coupon and price matching policy.  Here what they say:

Thank you for your email.

  • We accept one valid coupon per item purchased.
  • Our stores do not price match products.
  • We accept coupons issued by our Company and printed from our Company website http://www.metro.ca/
  • Unfortuneately, due to fraudulent activity with internet coupons, we do not accept coupons that are printed from any other websites, either on-line coupons or e-coupons.
  • We accept manufacturer coupons issued by Save.ca and Websaver.ca.  These coupons are ordered from the website and mailed to the Customer’s home.  These coupons are not printed from the internet.

Regards,

Metro  Customer Care

They only mentioned Save.ca and Websaver.ca as acceptable third party manufaturer coupons. I’m going to safely assume that Brandsaver.ca, GoCoupons.ca and coupons mailed to you directly from companies are also accepted.