A Look Ahead: This Week's ETFs to Watch

A calamitous week on Wall Street ended with stocks plunging on Friday, the 25th anniversary of the Black Monday debacle. Perhaps that was just a coincidence. Maybe it was not. Either way, U.S. stocks endured the worst one-day performance since June. The good news is Black Monday was not repeated last Friday because a 23 percent plunge for the Dow would equal 3,000 points.Concerns about global growth the pesky European sovereign debt crisis are once again ebbing to the forefront of investors' minds. Less-than-stellar earnings reports are not helping matters, either. On Friday, it was Dow components General Electric (NYSE: GE) and McDonald's (NYSE: MCD), among others, that roiled the market. On the bright side, yields on Italian and Spanish bond yields fell on Friday. The cautionary tale for the week ahead is that Asian shares are already pointing significantly lower as of Sunday evening. With that, here are just a few of the ETFs that will be in play in this week.U.S. Natural Gas Fund (NYSE: GAS)Ever volatile, the U.S. Natural Gas Fund finished Friday up almost 0.6 percent, but that was disappointing considering UNG traded up by as much as 1.5 percent during the session. Still, Friday's action highlights a positive about UNG that is often overlooked: A low correlation to equities.In fact, UNG's one-year correlation to the SPDR S&P 500 (NYSE: SPY) is negative 0.69. Predictions of cooler weather along the East Coast could also provide some near-term help to UNG.ProShares UltraShort FTSE China 25 (NYSE: FXP)The rebound in long China ETFs has plagued FXP over the past seven weeks. There is another side to the story. The aforementioned rally in China ETFs has been fast and furious with some of the funds jumping 10 percent or more in just one month. ETFs can remain overbought for extended periods of time, so there are no guarantees a significant pullback for China funds is in the works. However, many of these ETFs do look overbought. Friday's price action indicates as much so it would not be a bad idea to hedge a trade in a traditional long China ETF with FXP.Materials Select Sector SPDR (NYSE: XLB)An earnings play in the spotlight. The Materials Select Sector SPDR could see increased activity as top-10 holdings DuPont (NYSE: DD), Dow Chemical (NYSE: DOW) and Freeport McMoRan (NYSE: FCX) all report this week. The order is Freeport, DuPont and Dow. Those three stocks combine for 27 percent of XLB's weight.XLB is also a good gauge of risk appetite in the broader market. If the ETF falls below support at $36.50, selling pressure will likely intensify.Industrial Select Sector SPDR (NYSE: XLI)See above. With Caterpillar (NYSE: CAT), Boeing (NYSE: BA), 3M (NYSE: MMM) and United Technologies (NYSE: UTX) reporting this week, over 18 percent of XLI's weight is heading to the earnings confessional. All of these stocks are represent accurate temperature checks on the broader economy. Caterpillar's comments about domestic and global demand when it reports Monday could see the weekly deal for XLI. A good report from the construction equipment maker should boost XLI. If the alternative scenario comes to pass, then the alternative result will as well.For more on ETFs, click here.