Board Thread:Questions and Answers/@comment-5977347-20130514030454/@comment-1713281-20130514042437

Yes, and no; it's really a case by case thing. All monsters from the 40s-60s are inherently non-canon. They enter canon by a number of routes:


 * An entry in some Handbook or Index or other Marvel reference issue (Marvel Monsters: From the Files of Ulysses Bloodstone is a decent starting point)
 * Interaction with an established-canon character in their original Golden/Silver Age appearance
 * Reappearance and interaction with an established-canon character in a Copper/Bronze/Modern Age comic after their initial Golden/Silver age appearance

Some general rules of thumb though are that most of the Jack Kirby monsters have been brought into canon, as well as a majority of the monsters that appeared in Tales to Astonish, Strange Tales and Journey into Mystery.