They are mostly copper.
It would be worthwhile saving them if you get loads or are saving the planet single handed 
Rather than weighing them in, scrapyards will often do swaps of scrap for useful stuff off the 'pile'.
Much better than having to draw a cheque.
I've a slate at my scrappy![]()
My scrappy used to have bins/piles of useful stuff, last time I went there was very little, they had been broken into so get rid of stuff every few days now.

