What is NATO’s Article 4, could Denmark invoke it to protect Greenland from the US?

According to NATO,”Under Article 4 of NATO’s founding treaty, members can bring any issue of concern, especially related to the security of a member country, to the table for discussion within the North Atlantic Council.” Since the Alliance’s creation in 1949, Article 4 has been invoked nine times. Any member country of the NATO can formally invoke this article. As soon as it is invoked, the issue is discussed and can potentially lead to some form of joint decision or action on behalf of the Alliance.