Energy and material stocks didn't fare so well last week. Falling commodity prices were a big reason for the poor performance. Let's take a quick look at which commodities and producers where among the hardest hit, and what we can expect going forward.

Copper down 5.5%
The price of copper sunk last week as part of a general drubbing for commodities across the globe. This caused a free fall in shares of copper producer Freeport-McMoRan (NYSE:FCX), which were down about 8% for the week. As one of the world's top copper producers, it has a lot riding on the commodity, and while the company is diversifying into oil and gas, copper will continue to remain its mainstay. That's not a bad thing, for fellow diversified miner, BHP Billiton, sees a very compelling long-term fundamental outlook for copper with 1 million tonnes of additional production needed each year to keep up with demand.  

Silver down 4.7%
Despite a likely boost in sales of jewelry the week before from Valentine's Day, silver lost its luster last week. Among those feeling the weight of that fall were Silver Wheaton (NYSE:WPM). Its shares joined those of copper producer Freeport in falling more than 8% on the week. As a royalty streamer, Silver Wheaton benefits from the rise in the price of silver without facing the added risks of operating the mines from which the silver is produced. Unfortunately, that doesn't help much when silver prices plunge as they did last week. If you're a silver bull, then last week's sell-off could signify a nice buying opportunity. 

Crude down 4.5%
The sell-off in commodities wasn't just in metals, as it spilled over into crude oil and sent it down more than 4.5% for the week. This weighed shares of tiny Bakken-focused oil driller Kodiak Oil & Gas (NYSE: KOG) down about 4%. Kodiak, which reported a huge jump in its proved reserves and production last week, is still at the mercy of crude oil prices. Its full earnings report is expected on Feb 28; though, at this point in the company's growth cycle, earnings aren't as important as its ability to grow reserves and production.

Gold down 2.3%
Last week's slide in commodities didn't hit gold as hard as other shiny metals. That's one reason why shares of Goldcorp (NYSE:GG) were only down around 3%. Depending on your view of the underlying commodity, the weakness in gold over the past few months could be a big buying opportunity. Investors who are worried about inflation might want to start scooping up shares of gold producers before the rest of the market inflates those prices higher.

My Foolish take
If you're an investor that likes to wait for a sale before you start shopping, then last week's commodity price drubbing should get you excited. While its quite possible that these commodities have further to fall, the longer-term fundamentals appear to be very strong across the board. While gold's decline was tame last week when compared to other commodities, it has been particularly hard hit over the past few months. Now might be the best time to start digging into whether it is the time to add a gold stock for your portfolio.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.