Investing in mutual funds for retirement is never too late. And the Zacks Mutual Fund Rank can be an excellent tool for investors looking to invest in the best funds.

How can you tell a good mutual fund from a bad one? It's pretty basic: if the fund is diversified, has low fees, and shows strong performance, it's a keeper. Of course, there's a wide range, but using the Zacks Mutual Fund Rank, we've found three mutual funds that would be great additions to any long-term retirement investors' portfolios.

Let's take a look at some of our top-ranked mutual funds with the lowest fees.

Brown Advisory Flexible Equity Institutional (BAFFX Quick QuoteBAFFX - Free Report) has a 0.53% expense ratio and 0.43% management fee. BAFFX is classified as an Allocation Balanced fund, which seeks to invest in a balance of asset types, like stocks, bonds, and cash, and including precious metals or commodities is not unusual. With yearly returns of 13.03% over the last five years, this fund clearly wins.

Fidelity Advisor Global Commodity Stock A (FFGAX Quick QuoteFFGAX - Free Report) is a stand out amongst its peers. FFGAX is a Global - Equity mutual fund investing in bigger markets like the U.S., Europe, and Japan; these kinds of funds aren't limited by geography. With five-year annualized performance of 11.69%, expense ratio of 1.2% and management fee of 0.67%, this diversified fund is an attractive buy with a strong history of performance.

MFS Blended Research Core Equity R4 (MUEUX Quick QuoteMUEUX - Free Report) : 0.49% expense ratio and 0.4% management fee. MUEUX is part of the Large Cap Blend section, and these mutual funds most often invest in firms with a market capitalization of $10 billion or more. By investing in bigger companies, these funds offer more stability, and are often well-suited for investors with a "buy and hold" mindset. With a five-year annual return of 11.41%, this fund is a well-diversified fund with a long track record of success.

There you have it. If your financial advisor had you put your money into any of our top-ranked funds, then they've got you covered. If not, you may need to talk.