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.

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.

Let's break down some of the mutual funds with the top Zacks Mutual Fund Rank and the lowest fees.

Brown Advisory Sustainable Growth Investor (BIAWX Quick QuoteBIAWX - Free Report) : 0.79% expense ratio and 0.53% management fee. BIAWX 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. With annual returns of 13.52% over the last five years, this fund is a winner.

BNY Mellon Natural Resources I (DLDRX Quick QuoteDLDRX - Free Report) . Expense ratio: 0.89%. Management fee: 0.75%. DLDRX is a Sector - Energy mutual fund, which encompasses a wide range of vastly changing and vitally important industries throughout this massive global sector. This fund has managed to produce a robust 9.96% over the last five years.

Deutsche Science and Technology Institutional (KTCIX Quick QuoteKTCIX - Free Report) is an attractive large-cap allocation. With a much more diversified approach, KTCIX--part of the Sector - Tech mutual fund category--gives investors a way to own a stake in the notoriously risky tech sector. KTCIX has an expense ratio of 0.69%, management fee of 0.45%, and annual returns of 13.59% 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.