Yes, MONARCHS is a Scrabble word!

Letter values in Scrabble US: M 3, O 1, N 1, A 1, R 1, C 3, H 4, S 1.

Is it a valid word?

MONARCHS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a nation's ruler or head of state usually by hereditary right
large migratory American butterfly having deep orange wings with black and white markings; the larvae feed on milkweed

Also: crowned head, monarch butterfly, milkweed butterfly, danaus plexippus.