It is never too late to invest in mutual funds for retirement. As such, if you plan to invest in some of the best funds, the Zacks Mutual Fund Rank can provide you with valuable guidance.

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.

If you are looking to diversify your portfolio, consider DFA US Micro Cap Institutional (DFSCX Quick QuoteDFSCX - Free Report) . DFSCX is a Small Cap Blend mutual fund that usually targets companies with a market capitalization of less than $2 billion. This fund is a winner, boasting an expense ratio of 0.41%, management fee of 0.38%, and a five-year annualized return track record of 8.51%.

BNY Mellon Natural Resources I (DLDRX Quick QuoteDLDRX - Free Report) is a stand out amongst its peers. DLDRX is a Sector - Energy mutual fund, which encompasses a wide range of vastly changing and vitally important industries throughout this massive global sector. With five-year annualized performance of 18.44%, expense ratio of 0.9% and management fee of 0.75%, this diversified fund is an attractive buy with a strong history of performance.

Fidelity Select Software & IT Services (FSCSX Quick QuoteFSCSX - Free Report) . Expense ratio: 0.68%. Management fee: 0.64%. Five year annual return: 14.41%. With a much more diversified approach, FSCSX--part of the Sector - Tech mutual fund category--gives investors a way to own a stake in the notoriously risky tech sector.

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.