You've got 17 Pokemon, 19 Trainers and you'll probably end having about 9 Energy. That leaves 15 extra slots. I'll help you fill those in.
The aim of your deck probably should be to stream attackers by powering them up with Bronzong.
-1-1 Metagross (You don't want to be including a stage two line like this as the likelihood of you getting it out is very low, and you lose a lot of consistency in getting out your Bronzong, M-Scizor and Jirachi.)
-1-1 Noctowl (Basically the same deal as Noctowl)
-2 Shauna (It's not really good enough to warrant a full four, so lets use this space for other supporters.)
-1 Switch (You don't need 3 Switch.)
-1 Escape Rope (You don't need 3 Escape Rope either.)
-1 Rare Candy (No need for this without Metagross.)
-2 Energy Retrieval (You don't need this in your deck.)
+1-1 Bronzong PHF (This gives you a lot more consistency and assistence for your deck, which will be nice!)
+1 Aegislash-EX (Aegislash is really nice as it prevents any Pokemon with Special Energy from damaging it, which is used is most decks.)
+4 VS Seeker (This is a great card! You'll definitely want to include it.)
+3 Muscle Band (This is also a great card, since it can boost your final damage output!)
+3 Battle Compressor (Discarding cards from your hand may not seem all too great at first... but this card allows for you to get your Metal Energy into your discard pile so you can Metal Links it with the Bronzong.)
+1 Lysandre (A really nice card for any deck.)
+9 Metal Energy (Can't forget the Energy!)
+2 Steel Shelter (Steel Shelter is nice Stadium for Metal Types, as it prevents them from being poisoned or put to sleep through cards that are becoming increasingly common.)
+1 Xerosic (You'll likely end up facing Garbodor, which prevents the use of Abilities. We're not going to like that, so we can include Xerosic to remove the tool it needs to activate.)