Copper's steep decline over the past 2 weeks has brought it to a critical level. A clear move below trend line support here would mean a break out of a well established triangle.
Weakness in the Asian session today puts a break during the London or US sessions into play.
I've shown this situation on the weekly chart to give a longer term perspective.
The recent move below the 40 week (200 day moving average) plus the fact that the slow stochastic is in full flight after a break out of the overbought zone both support the potential for a move lower if the triangle support is broken.
A typical stop entry strategy applying a price filter of a bit over 1/2% of copper's value once the trend line breaks would mean selling if price falls to around 349.50.
The measuring rule, where the height of the triangle is projected from the break out point is often used as a profit target with triangle strategies. I've used Tracker's Fibonacci price tool for this. This is the 100% level on the chart and sets a measuring target at around 278.0
If there is a setup, I'll post a follow up discussing stop loss strategies.