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.

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

Fidelity Advisor Stock Select Allocation Cap A (FMAMX Quick QuoteFMAMX - Free Report) : 0.79% expense ratio and 0.48% management fee. FMAMX 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 annual returns of 14.29% over the last five years, this fund is a winner.

Thornburg Global Opportunities A (THOAX): 1.29% expense ratio and 0.84% management fee. THOAX 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 yearly returns of 16.3% over the last five years, THOAX is an effectively diversified fund with a long reputation of solidly positive performance.

Segall Bryant & Hamilton International Small I (SBSIX): 1.06% expense ratio and 0.9% management fee. SBSIX is a part of the Non US - Equity fund category, many of which will focus across all cap levels, and will typically allocate their investments between emerging and developed markets. With a five-year annual return of 14.4%, 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.