Its acts by inhibition of elongases and of the geranylgeranyl pyrophosphate (GGPP) cyclases, which are part of the gibberellin pathway.

It is used for grass and broadleaf weed control in corn, soybean, peanuts, sorghum, and cotton.

The (R)-enantiomer is less active, and modern production methods afford a higher concentration of S-metolachlor, thus current application rates are far lower than original formulations.

[5] The United States Environmental Protection Agency (US EPA) has classified Metolachlor as a Group C, possible human carcinogen, based on liver tumors in rats at the highest dose tested (HDT).

Cell division in yeast was reduced,[12] and chicken embryos exposed to metolchlor showed a significant decrease in the average body mass compared to the control.