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.

abrdn Emerg Markets ex-China Instl (GWLIX) has a 0.94% expense ratio and 0.75% management fee. GWLIX 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 12.74% over the last five years, this fund clearly wins.

Goldman Sachs Intl Tax ManagedEq R6 (GHTRX Quick QuoteGHTRX - Free Report) : 0.89% expense ratio and 0.85% management fee. GHTRX 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. GHTRX, with annual returns of 11.96% over the last five years, is a well-diversified fund with a long track record of success.

T. Rowe Price US Large-Cap Core Adviser (PAULX) is an attractive large-cap allocation. PAULX 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. PAULX has an expense ratio of 0.97%, management fee of 0.53%, and annual returns of 11.16% over the past 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.