Normalized corrected templates for an early (M1.0), mid (M3.0), and late (M6.0) subtypes. The templates are labeled according to MC (to the left), with metallicity decreasing from super-metal-rich dwarfs (class 0.5) to ultra-metal-poor subdwarfs (class 12.5). The relative strengths of different absorption lines change with metallicity (i.e., the CaH absorption band around 6800 Å becomes more prominent at extremely low metallicity, and the TiO band around 7100 Å gradually weakens.)