Cars are mostly metal.

汽车大多是金属制成的。

《柯林斯英汉双解大词典》

It's mostly metal, but there's a little wooden handle, too.

大部分是金属，但是有一个小巧的木制把手。

youdao

Their weightless-looking structures were mostly made of glass and metal.

VOA: special.2009.12.13

There's an important distinction between these two types of objects: Comets are mostly water, ice and dust, while asteroids are mostly rock or metal.

CNN: While you were working: An asteroid just flew by

In the nineties, a range of American acts began drawing from the work of Norwegian metal bands that were famous mostly for a look and for several unpleasant events.

NEWYORKER: The Dark Arts

Investors should expect depressed results, mostly impacted by lower iron ore prices and a lack of contribution from its base metal division, which should remain in the red.

FORBES: For Brazil's Vale, A Case Of Lowered Expectations