You didn't expand into bottom right corner at all, didn't capture metal spots fast enough. Watch how your opponent expands.

Your artillery (lance) were idle most of their lifetime. Hovers have one of the cheapest scouts, combined with lance you can take out buildings (like enemy stinger protecting metal spots) with ease. Use hold fire, get in range and choose big targets.

You never captured your geothermal vent and didn't make enough energy buildings for your metal income.