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.

Thornburg Investment Income Builder A (TIBAX): 1.12% expense ratio and 0.69% management fee. TIBAX is an Allocation Balanced mutual fund. Allocation Balanced funds look to invest across asset types, like stocks, bonds, and cash, and including precious metals or commodities is not unusual; these funds are mostly categorized by their respective asset allocation. TIBAX has achieved five-year annual returns of an astounding 15.24%.

Janus Henderson Global Research I (JWWFX). Expense ratio: 0.82%. Management fee: 0.7%. JWWFX 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 This fund has managed to produce a robust 12.54% over the last five years.

MFS Blended Research Value Equit R3 (BRULX Quick QuoteBRULX - Free Report) . Expense ratio: 0.71%. Management fee: 0.25%. Five year annual return: 12.73%. BRULX is a Large Cap Value mutual fund, which invests in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value.

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.