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 investors' portfolios.

Let's break down some of the mutual funds with the top Zacks Mutual Fund Rank and the lowest fees.

T. Rowe Price Capital Opportunity R (RRCOX) has a 1.16% expense ratio and 0.32% management fee. RRCOX is classified as a Large Cap Blend fund. More often than not, Large Cap Blend mutual funds invest in companies with a market cap of over $10 billion. Buying stakes in bigger companies offer these funds more stability, and are well-suited for investors with a "buy and hold" mindset. With yearly returns of 13.89% over the last five years, this fund clearly wins.

Neuberger Berman Large Cap Value Institutional (NBPIX): 0.6% expense ratio and 0.57% management fee. NBPIX is a part of the Large Cap Value category, and invests in equities with a market capitalization of $10 billion or more, but whose share prices do not reflect their intrinsic value. NBPIX, with annual returns of 10.63% over the last five years, is a well-diversified fund with a long track record of success.

Eaton Vance Emg & Frontr Cntrys I (EICOX Quick QuoteEICOX - Free Report) . Expense ratio: 1.15%. Management fee: 0.98%. Five year annual return: 15.23%. EICOX is a Non US - Equity fund. Many of these funds like to allocate across emerging and developed markets, and will often focus on all cap levels.

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.