Bangalore houses what might be an outsize share of India’s metal heads, so it’s appropriate that this was the city that thrash metal band Slayer picked for their first show in India. The band played in one of the city’s outlying suburbs, and drew a crowd from all over, including Vietnam, as they played a set list that stretched back through albums such as “Reign in Blood,” to “Show No Mercy,” their debut album from 1983.