Between most metals tasting "sweet" and the mouth being a baby's foremost sensitive way of accruing information about something, babies and small kids are insti

Between most metals tasting "sweet" and the mouth being a baby's foremost sensitive way of accruing information about something, babies and small kids are instinctively driven to put anything and everything in their mouth if it fits and consider metals as food until sternly educated otherwise. It takes a long time before any of the other senses become mature enough to be (more) useful avenues of accruing information and parents can finally stop worrying about it.