I wonder if the material of all the stuff in our sun's orbit would be sufficient to build a dyson sphere. Afaik, 99% of the mass of our solar system is the sun itself...
Lets assume energy converting photovoltaics will be made of non-crystalline materials with a high light absorption coefficient allowing solar cell thickness of ~100 nm = 100e-9 m.
Sphere surface is 4pir^2, in our case 43.14150e9^2 = 3e23 m2 * 100e-9 m = 3e16 m3 is the total volume occupied by a Dyson swarm tech.
For comparison the volume of matter that Earth contains is 1e21 m3, which is 1e21/3e16 ~= 1e5 = 100,000 times larger than what is required for a Dyson swarm.
Sci-fi but mostly in the ’not melting down’ part.
Earth, Mars and Venus each have about 10x the iron of Mercury. The asteroid belt is inconsequential.
If you consume all the iron core planets, you have about 5 cubic centimeter of iron to play with for each square centimeter of dyson sphere area.
There's a lot of unknowns for the gas giants, particularly what % of them contains iron, but Jupiter /might/ have as much as 100x earth heavy elements (including iron), but these would be at its core, and its not totally clear how you would extract them.
I think the key question is what sort of stresses you expect the sphere to be under, and thereby what materials and tensile strengths are required. It would not surprise me if the stress is basically nil (in theory you could orbit a sphere made of iron dust?) or totally infeasible for iron.