Special moves options are Power Gem, Ancient Power, Hidden Power, Hyper Beam, Solar Beam, Psychic, Charge Beam, Dazzling Gleam.
The movepool is really weak, aside from power Gem. HP fire for Scizor on the switch-in i guess. Charge Beam could be used against bulky water types and would allow you to boost even more but is useless against water/ground ones. Dazzling Gleam must be run i think, if it had a special flying move it would provide better coverage but unfortunately...
It reaaally lacks Earth Power, it would be so good. Maybe Grass Knot too.
If you want to go "almost fully special" you could run PG/DG/EQ, for almost the same coverage as the physical set.
Naive 4EV +2 EQ does like 70-80% to standard Metagross-M.