Metal detectors cannot be used in many cases because landmines can be made of non-metal materials.

VOA: special.2010.05.03

It's made of strong metal, it's got very thin slits to be able to see straight ahead, covered up; everything else is covered up, a good one will cover your neck as well.

头盔是坚固的金属制成,正面有一条很细的开口能让士兵看到前方,左右两边都包住,剩下所有地方都包住,好一点的头盔甚至能保护颈部

耶鲁公开课 - 古希腊历史简介课程节选

These replacement joints can be made of combinations of metal alloys, plastic and ceramic, but new research shows that it might be possible to regenerate damaged joints using a patient's own stem cells.

VOA: standard.2010.08.11