Collectibles (Gold coins) held one year or longer are taxed at 28% as capital gains.
If done wrong, yes. However retirees can put money into a Gold IRA and it becomes a tax shelter.
You can put gold bars in there, but they can be confiscated by US government under certain circumstances - so I don't advise keeping gold bars. But they do qualify for use in a tax sheltered gold IRA.
Caveat, only high value collectable US Gold coins (purity of 24 karat) and 22 karat US Gold Eagles are the only coins allowed in a tax sheltered Gold IRA - and they can't be confiscated by US government.