The U.S. Mint has implemented a rule against melting down pennies and nickels which, at current metal prices, could be worth more as metal than as currency.
From a page right out of the history books, it used to be not uncommon for people to melt down coin when we were on a gold and/or silver standard. People could also bring metal in to have it minted when the coin was worth more than the metal. So, suddenly, we’ve come full circle through fiat back to melting down coins again. Only this time, it’s illegal, in spite of the fact that its a traditional American value, melting coins.