Grey nuggety items I have found include melted beer cans, melted carbon-zinc battery cases, detonators, weld spatter, oxycutting spatter, retort & smelter slag inclusions, electrical solder, old can solder, plumbers solder spatter, bismuth shot.. It is wonderful what a bushfire/rubbishfire/campfire/mine workshop will make.
There a quite a lot of simple tests to ID most common MD metal nugget finds without resorting to density tests, which are difficult with small nuggets.
You do need to go through these tests in order else conclusions will be wrong.
1) If strongly attracted to a rare earth magnet then most likely carbon steels or 400 series stainless steel. Slightly magnetic can also be a bunch of stuff, mostly valuless, but rarely, iron coated gold. If in doubt hit with hammer & centre punch. Gold will indent & iron coating flake off. Non magnetic metal is interesting so we keep testing.
3) If you can dent /mark it with your fingernail then it is lead or tin. 99.99% of grey finger markable metal is lead. Alloyed lead can be harder than fingernail though.
3) Put a decent knife edge on it & press and draw. If can groove it then is a soft metal eg bismuth, copper, lead, bronze, brass, tin, silver, gold, platinum.(Pt is harder than pure gold or silver but not as hard as most 18-14k gold). If nonmagnetic & you cant mark it at all with a decent knife or file then most likely heat treated 300 series stainless steel or VERY unlikely, tungsten.
4) If can mark at all with a knife then scrape it with decent fine cut file. If scrapes easily & scraped surface is coloured then should be easy enough to figure out (brass,bronze, gold, copper).
5) if scraped surface is silvery then scrape a few square mm clear & chuck the whole thing in brick acid (30% HCl). If bubble wells then probably alu or zinc based. If slow fine bubbles form & the silvery streak dulls to darker grey after 5 min then probably bismuth, tin or lead based. If after 5 min the streak stays silvery & no bubbles then might be silver or platinum. If in doubt leave overnight & check again.
6) Boil some water & put an inch or two in a bowl and place it somewhere safe outside. Stand the jar with the brick acid & nugget in the bowl of hot water to warm it. Go a long way away for a couple of hours until cools and fumes gone. Silver will dull and whitish powder will be present but if streak still shiny & no powder present then might be platinum.
7) Stick a hot soldering iron on the scraped surface for a few minutes. Soldering iron is 350C, lead melts at 327C, tin 231C & silver 961C, platinum 1768C so if melts even a little then not silver or platinum. If nugget too large for a soldering iron to heat then use a butane brulee torch on the edge of the piece. Even though technically 1300C flame there is no chance you will heat the nugget anywhere near that temp in just a few minutes but it will get edge to 350C pretty quick.
8) If grey metal, non magnetic, marks with knife, doesnt react with HCl or melt easily with butane flame then clean nugget with toothbrush & rinse thoroughly then drop in hydrogen peroxide ( 3% from chemist) if bubbles ferociously then probably platinium - Yay ! Time to take it to buyer for XRF.
layful: 
