how can i improve metal in render ? make it more realistic? grey metal piece in foreground is supposed to be aluminum material.
scene Light setup, background environment (sky dome) corona sun
see attached
Hello,
A good start would probably be to post your current material settings 
Choose interesting environment map so it can reflect at metal, make less gloss to see reflection, and rotate envirometn if needed. You can add small bump with big noise to distort reflection, also you may add dirt map to gloss slot
As you were already told, no highly reflective material will look good if it doesn’t have something to reflect. Put contrasty HDRI map into enviroment or reflection override and your metal should shine in different colours.
FYI, that metal is not PBR (physically based rendering) compliant. Metallics should have zero diffuse, then any dielectric material (dirt/dust/paint) needs to be applied as a layer on top that has white in the reflection colour.