Many of the traditional brokerage companies, like Schwab, Fidelity, etc., do not let you trade futures in your IRA account. However, you can trade options on stocks and ETFs in your IRA. 401 Ks usually have a very limited number of mutual funds that you can invest in. However, if you leave your job, you can roll your 401K into an IRA to vastly increase your investment options. If you are self-employed, there are several other options mentioned by other posters above.
If you want to trade futures in your IRA, you have to open a self-directed IRA. Just ask your futures broker what companies they work with.
I opened a self-directed IRA with Equity Trust Company. I can trade futures, but a percentage of the profit is taxable because you trade futures with margin. Margin is like a loan, so whatever profit you make from the margin portion is taxable, because it is not IRA money. Self-directed IRAs also let you invest in other unconventional activities such as real estate, tax liens, private loans, etc. However, there is some education involved to make sure you do everything legally and handle any potential taxes properly.