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.

The easiest way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. Using the Zacks Mutual Fund Rank of over 19,000 mutual funds, we've identified three outstanding mutual funds that are ideally suited to help long-term investors pursue and achieve their retirement investing goals.

Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.

BNY Mellon Natural Resources A (DNLAX Quick QuoteDNLAX - Free Report) has a 1.13% expense ratio and 0.75% management fee. DNLAX is a Sector - Energy mutual fund, which encompasses a wide range of vastly changing and vitally important industries throughout this massive global sector. With yearly returns of 15.16% over the last five years, this fund clearly wins.

Fidelity Fund K (FFDKX Quick QuoteFFDKX - Free Report) . Expense ratio: 0.37%. Management fee: 0.31%. FFDKX 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. This fund has managed to produce a robust 10.56% over the last five years.

MFS Mass Investors Growth Stock R2 (MIRGX Quick QuoteMIRGX - Free Report) is an attractive large-cap allocation. MIRGX is a Large Cap Growth mutual fund, and these funds invest in many large U.S. firms that are projected to grow at a faster rate than their large-cap peers. MIRGX has an expense ratio of 0.96%, management fee of 0.33%, and annual returns of 11.98% 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.