What are the best chemical liquids to clean metallic surfaces?
Assuming clean means anti-pathogenic, I would use Hydrogen Peroxide "oxyclean" since it can "clean" metals by removing pathogens. $\ce{H2O2}$ is marketed in various strengths. 1% dilution can kill up to 99.99% bacteria in 30 seconds.

Any butyl based cleaning product is a very good degreaser but it may harm rubber products.

Check here and here for more.