I don't really agree with the strut mount. If you've ever been in an e36 when it goes it's more of a solid thud than clanking. I do have a metal clanking noise that fits your description. My friends shop put it up on a lift and thought it was a loose heat sheild. Haven't gotten around to removing the heat shield to find out though.
I'd suggest putting the car up on ramps/jack-stands, and like someone mention above, start tapping around with a rubber hammer.