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.

Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.

Calvert Equity Portfolio A (CSIEX Quick QuoteCSIEX - Free Report) has a 0.91% expense ratio and 0.55% management fee. CSIEX is a Large Cap Growth option; these mutual funds purchase stakes in numerous large U.S. companies that are expected to develop and grow at a faster rate than other large-cap stocks. With yearly returns of 12.84% over the last five years, this fund clearly wins.

BNY Mellon Natural Resources A (DNLAX Quick QuoteDNLAX - Free Report) : 1.14% expense ratio and 0.75% management fee. DNLAX is a Sector - Energy fund, which are comprised of various changing and hugely important industries throughout the massive global energy sector. DNLAX, with annual returns of 14.25% over the last five years, is a well-diversified fund with a long track record of success.

GMO Quality III (GQETX Quick QuoteGQETX - Free Report) : 0.49% expense ratio and 0.48% management fee. GQETX is a Large Cap Blend fund, targeting companies with market caps of over $10 billion. These funds offer investors a stability, and are perfect for people with a "buy and hold" mindset. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 10.94% over the last five years.

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.