Read as a working part of a chart rather than as a character sketch, Mesha is defined by four things that a jyotishi checks before anything else: who owns it, who is strong in it, who is weak in it, and which lunar mansions cross it.
Mangala, Mars, owns Mesha. Wherever Mesha falls among the twelve bhavas, the condition of Mangala is the condition of that house, and the affairs of the house are read through him. This is the single most consequential fact about the sign, because it means Mesha never stands alone; it is always a pointer to a planet elsewhere in the chart.
Surya, the Sun, reaches exaltation in Mesha, and the classical texts give the exact point as the tenth degree. Shani, Saturn, falls to debilitation in the same sign, with the twentieth degree given as the low point. The pairing is not accidental. Exaltation and debilitation are arranged so that a planet and its natural opposite occupy opposed conditions, and the Sun and Saturn are treated throughout jyotisha as antagonists. A chart with the Sun near ten degrees of Mesha and one with Saturn near twenty degrees are being read on the same axis from opposite ends.
Three nakshatras cross the sign. Ashwini and Bharani lie wholly within it, and the first quarter of Krittika falls at its end, the remaining three quarters passing into Vrishabha. Because the nakshatra divisions do not align with the sign divisions, a planet in late Mesha sits in a mansion that mostly belongs to the next sign, and readings that use the nakshatra and readings that use the rashi will emphasise different things about the same degree.