Effect sizes can be log transformed on the fly. This is convenient when meta-analyzing odds ratios. In this case, two studies have the same direction of effect if their log(odds ratio) statistics are both positive or negative, corresponding to odds ratios that are both >1.0 or <1.0.
This transformation is activated through the EFFECTLABEL command. For example, EFFECTLABEL log(ODDSRATIO) instructs metal to log-transform the ODDSRATIO column prior to analysis.