Robots work off of framework and joints controlled by actuators (linear drives, hydraulics, motors, peizo's, servos, etc), where BattleMechs just simply replace these with Myomer musculature, just like human/oid physiology. If using human anatomy as a basis and substitute synthetic / metallic colors, you'd be just fine.
To represent this on a miniature scale, you could use balsa or styrene strips, pewter sprue (use clippers then file flat), or pieces of flat toothpick and glue into a cage-like formation, then fill in-between with parts, floss or 20-22g stranded electrical wire would work well for Myomer. If you have any damaged/broken electronics, you could probably find some tiny diodes and components... If you're going for 'damaged' and/or 'in repair', don't de-solder, just use some dykes and clip them off or in half ;)
IF you're good with soldering (OR would like to learn/practice), building a structure with pewter sprue would work great because tin-based solder will hold better than glue.
For concept, consider the Descent Stage for the Mars Science Laboratory... Here's an image without any "armor" (external components):
