Here is the SPDR® S&P Metals and Mining ETF (NYSE:XME), which has demonstrated its overhead supply by way of that upper horizontal line:
As you can see from many years of data, this instrument definitely has the ability to top and fall.
As the ratio chart below suggests, XME’s explosive rally versus the VanEck Gold Miners ETF (NYSE:GDX) is very long in the tooth, which I believe improves the likelihood that XME is in for some weakness.