I use a cheap ($2-aus) bonding agent with names such as 'Bond-Crete' or this one in the photos is 'KS Bond'. You can find this type of glue at any "Cheap" or discount store. (ie: The $2 Shop, The Reject Shop, etc.) I use this glue to adhere metal to almost everything.  I make my own jewelery and I have not had one glued item come unstuck yet. And I've been using this type of glue for as long as I remember. I have used this glue on items fit my 'Fairy Garden' which have sat outside for over 2 years. The glue is still holding, even after rain, freezing temperatures and moss growing over everything. 

Description reads: Strong adhesive. Chloroprene cement. Use: Bonding vulcanised rubber and leather.  Metal, stone, glass, porcelain,  sponge, paper, textiles, wood and plastic to themselves or each other.  

[![https://i.sstatic.net/TSHpz.jpg][1]][1]


  [1]: https://i.sstatic.net/TSHpz.jpg