The eight-year-old bull market isn't ending anytime soon, investment expert Jerry Castellini told CNBC on Wednesday.
In fact, he still believes the market is still in the early stages of the bull cycle.
"There's just too many indicators that suggest our economy in the U.S. has still got further to go [and the] global economy's just getting started," the president and chief investment officer at CastleArk Management said in an interview with "Power Lunch."
The market's rally has mainly been powered by a small number of stocks, while about two-thirds of the market hasn't really discounted a broader economic recovery, he explained.
"That's really what sits behind really the value and the attractiveness of the market," Castellini said. "What's really lurking out there is this phenomenal bull market that still hasn't happened for the majority of stocks and that's what we think you're going to see happen and evolve over the next six months."
Marc Faber, on the other hand, believes "we have a bubble in everything."
The editor of The Gloom, Boom & Doom Report told "Fast Money Halftime Report" on Wednesday that even if the dropped 20 percent, it still wouldn't make him bullish on the U.S. stock market.
Stocks fell on Wednesday, the last trading day of May. However, the Dow Jones industrial average, S&P and Nasdaq were all on track to post monthly gains. The tech-heavy Nasdaq was up 2.57 percent for the month entering the session and was on track to record a seven-month winning streak, its longest since 2013.
Richard Bernstein, a CNBC contributor and CEO of Richard Bernstein Advisors, believes people are becoming momentum investors.
"People were never really bulled up. They were never really confident, and the first quarter weak patch just reinforced their fears, which began this huge momentum trade, I would argue, into defensive positioning either in the bond market or the stock market," he told "Power Lunch."
He believes that's misguided right now.
"There is an increasing amount of data showing that we're past that weak patch, but, be that as it may, the market's the market," Bernstein said.
—CNBC's Tae Kim and Fred Imbert contributed to this report.