Question

I have some unknown metal. How to find out what it is?

Answer 1

You could determine its density and its specific heat capacity. Then compare your values to known values for the density and specific heat capacity of metals.

Here is a procedure to do this. (For specific heat, m means mass in grams, DT means change in temperature in degrees C, and `"C"_"p"` means specific heat in `"J/g·"^("o")"C""`):
http://www.dbooth.net/mhs/chem/specificheat.html

This is a link to an interactive periodic table from the Royal Society of Chemistry. It has the accepted density for all elements in `"g/cm"^3"`, and specific heat in `"J/kg·K"`. To convert to `"J/kg·K"` to `"J/g·"^("o")"C""`, divide by 1000.
http://www.rsc.org/periodic-table

Answer 2

A way would be to try and dissolve a small piece of the metal in different acids.

(1) If the metal reacts with water, you can think in the direction of `Na, K` or even `Ca,Ba`. Hydrogen is given off.

(2) If you can dissolve it in diluted acid, it's a non-noble metal like `Zn,Al,Fe`. Usually hydrogen bubbles appear.

(3) If you need an oxidising acid like sulfuric or nitric acid, the metal is nobler. Think `Cu,Ag`. Usually fumes of `SO_2` (in case of sulfuric acid), or `NO_x` (from nitric acid) will be given off

(4) If even that doesn't work, you're dealing with the real noble metals like `Au` or `Pt`, that will only 'dissolve' in aqua regia, a mixture of concentrated nitric and muriatic acid.

After dissolving, there are numerous precipitation tests to determine the exact kind of metal.