A rubber ball and a chrome ball undoubtedly have different textures from each other. The difference between material's textures is derived from their surface characteristics, which is commonly modelled via specular and diffuse values.

A rubber ball has a rough non-reflective surface, which reflects light evenly towards all directions (diffused reflection). Therefore, it looks shiny as a whole but it has weak contrast and narrow value range.

On the other hand, a chrome ball has a smooth reflective surface, which reflects light towards one direction (specular reflection). Therefore it looks dazzling at certain angles and has a conspicuous bright spot. It also has sharp contrast and broad value range.

Giving metallic characteristic to a sphere and a cylinder, they can be drawn as follows.

Tips
In a drawing of a metallic object, the most important thing is a bold arrangement of dark tones and bright tones. Unless a drastic change in value is introduced at the proper points in the curved surfaces or the borders of sides, the object will never look metallic.

It is impossible to describe the reflection accurately, however, the following way can make an illusion of a reflection.

1. Emphasize the highlight by putting dark tones around it.
2. Express the image reflected in the object with dark tones and concentrate the darkest tones near the center.
3. Make the shadowed side as light as possible by drawing the reflected light.

Examples
Here are some examples of metallic objects.

© Igarashi Susumu