There is never a wrong time to invest in mutual funds for retirement. So, if you're still looking for the best mutual funds, the Zacks Mutual Fund Rank can be a great guide.

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.

Fidelity Trend Fund (FTRNX Quick QuoteFTRNX - Free Report) has a 0.74% expense ratio and 0.73% management fee. FTRNX 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 yearly returns of 16.33% over the last five years, this fund clearly wins.

PGIM QuantSolutions Mid-Cap Value Z (SPVZX): 0.88% expense ratio and 0.73% management fee. SPVZX is a Mid Cap Value mutual funds that aims to target medium-sized companies that possess strong value and income opportunities for investors. With yearly returns of 10.26% over the last five years, SPVZX is an effectively diversified fund with a long reputation of solidly positive performance.

VALIC Co I US Socially Responsible (VSRDX). Expense ratio: 0.35%. Management fee: 0.25%. Five year annual return: 11.84%. VSRDX is classified as a Large Cap Blend fund. More often than not, Large Cap Blend mutual funds invest in companies with a market cap of over $10 billion. Buying stakes in bigger companies offer these funds more stability, and are well-suited for investors with a "buy and hold" mindset.

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.