Complex sentence: The metallic bond eliminates the possibility for transition metal elements (or alloys) to be classified as transparent materials, although there is an aluminium oxide called Aluminium oxynitride, which is transparent and stronger than glass.
Split into simpler sentences: The metallic bond eliminates the possibility for transition metal elements (or alloys) to be classified as transparent materials. Transparent compounds that include aluminium are possible, for example there is an aluminium oxide called Aluminium oxynitride, which is transparent and stronger than glass.