Thanks for sharing your list glad to see Neo Destiny and Skyridge on top
The Siegemaster can become a powerful threat in Voltron/aura builds, or decks that have extra combat steps
Well walk you through the best of them and help you decide whether this set is right for you
I can only think of a handful right now (Djinn Illuminatus, Harness the Storm, Frankie Peanuts, Cloudstone Curio, and Tooth and Nail) and there have been times when Spikes have messed up Tooth and Nail by grabbing some game ending combo or accelerating it off major Urzatron lands or other quick mana ramp, and then use something that prevents it from being countered (like Boseiju, Who Shelters All)
So after knowing that, and reading the overview section of this post, I would not recommend using Metang with Beldum unless you plan on using Metagross as well