Investing in mutual funds for retirement is never too late. And the Zacks Mutual Fund Rank can be an excellent tool for investors looking to invest in the best funds.

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 take a look at some of our top-ranked mutual funds with the lowest fees.

Northern Active M Intlernational Equity (NMIEX): 0.84% expense ratio and 0.82% management fee. NMIEX 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. NMIEX has achieved five-year annual returns of an astounding 10.17%.

Victory Pioneer Global Equity A (GLOSX Quick QuoteGLOSX - Free Report) . Expense ratio: 1.11%. Management fee: 0.65%. GLOSX is a Global - Equity mutual fund, which invests their assets in large markets, leveraging the global economy. This fund has managed to produce a robust 15.4% over the last five years.

Goldman Sachs Tax Managed Equity IR (GQIRX): 0.77% expense ratio and 0.64% management fee. GQIRX is part of the Large Cap Blend section, and these mutual funds most often invest in firms with a market capitalization of $10 billion or more. By investing in bigger companies, these funds offer more stability, and are often well-suited for investors 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 13.24% over the last five years.

These examples highlight the fact that there are some astonishingly good mutual funds out there. If your advisor has you in the good ones, bravo! If not, you may need to have a talk.