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.

MainGate MLP Fund I (IMLPX Quick QuoteIMLPX - Free Report) has a 1.45% expense ratio and 1.25% management fee. IMLPX is classified as a Sector - Energy mutual fund. Throughout the massive global energy sector, these funds hold a wide range of quickly changing and vitally important industries. With yearly returns of 25.57% over the last five years, this fund clearly wins.

Thornburg Global Opportunities I (THOIX) is a stand out amongst its peers. THOIX is a Global - Equity mutual fund. These funds invest in large markets like the U.S., Europe, and Japan, and operate with very few geographical limitations With five-year annualized performance of 14.17%, expense ratio of 0.99% and management fee of 0.83%, this diversified fund is an attractive buy with a strong history of performance.

1290 Avantis US LargeCap Growth I (TNXIX): 0.65% expense ratio and 0.5% management fee. TNXIX 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 a five-year annual return of 10.86%, 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.