The reason why metal have to be clean with sandpaper is to remove the oxide layer on the surface of the metal. This is because most metal have a high tendency toward oxygen. The metal will react with oxygen in the air and form an oxide layer on the surface of the metal.
To avoid rusting
Fine sawdust occurs when wood is sandpapered.
what are the characteristics of metals? metals? non-metals?
metals
They are metals.
Alkali metals are very reactive metals.
They are in between the metals and non metals
You can see the Alkaline Metals, Alkaline Earth Metals, Transition Metals, Other Metals (poor conducting metals), metaloids (characteristics of metals and non-metals combined), non-metals, noble gases, and unknown metals (like #112-118)The transition metals at the bottom of the periodic table are lanthanides and actinides.3 main ones are usually: Alkaline metals, Transition metals, and Non-metals...I hope this was useful!-Fuyuki
I believe that the answer you are looking for is Transition Metals.
metals
Non metals
Non metals