What: Shares of Brazilian miner Vale SA (NYSE:VALE) jumped 11% late in trading on Friday, as investors speculated about the future of the company, Brazil, and interest rates.

So what: Brazilian stocks, in general, rose today, as metals prices were higher, and investors bet the Federal Reserve wouldn't raise interest rates soon. Iron ore prices climbed, as well, after a rough past three months for the commodity. 

There was also speculation that CEO Murilo Ferreira will be ousted as part of the political upheaval taking place in Brazil. Ferreira took the job in 2011 as President Dilma Rousseff took power. Now that she's been ousted from power, Vale may be looking for a new leader. 

Now what: Metals stocks have been incredibly volatile this year, and Vale's shares are showing the ups and downs, as well. But investors shouldn't focus too much on this short-term speculation, and should look at the long-term trends. We're seeing the metals market oversupplied by Asian competitors, and demand in Asia simply isn't keeping up. That's led to falling commodity prices, including iron ore. It's that weakness that would keep me out of the stock, even if the news hitting the wires is mildly positive today.

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.