In trading on Monday, shares of the SPDR S&P Metals and Mining ETF ( XME) entered into oversold territory, changing hands as low as $39.15 per share. We define oversold territory using the Relative Strength Index, or RSI, which is a technical analysis indicator used to measure momentum on a scale of zero to 100. A stock is considered to be oversold if the RSI reading falls below 30.In the case of SPDR S&P Metals and Mining, the RSI reading has hit 28.7 — by comparison, the RSI reading for the S&P 500 is currently 64.5. A bullish investor could look at XME's 28.7 reading as a sign that the recent heavy selling is in the process of exhausting itself, and begin to look for entry point opportunities on the buy side. Looking at a chart of one year performance (below), XME's low point in its 52 week range is $36.20 per share, with $44.20 as the 52 week high point — that compares with a last trade of $39.17. SPDR S&P Metals and Mining shares are currently trading down about 3.2% on the day.