Yes, SIMILES is a Scrabble word!

Letter values in Scrabble US: S 1, I 1, M 3, I 1, L 1, E 1, S 1.

Is it a valid word?

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

a figure of speech that expresses a resemblance between things of different kinds (usually formed with `like' or `as')