Reaction of organometallics with epoxides

Grignard and organolithium reagents will also react with epoxides, attacking the less hindered carbon .

Being a strong nucleophile, the organometallic attacks the epoxide from the less hindered end of the epoxide ring.  Note that in the product, the new C-C bond is made to the carbon neighboring the alcohol carbon.  (In contrast, when organometallics add to carbonyls, the new C-C bond ends up directly bonded to the alcohol carbon.)