Opara scored 70 in snatch; and 92 in clean and jerk for total 162 points.
India’s Sanjita Chanu won the gold with 173 points, while her compatriot, Saikhom Mirabai, won silver with 170 points.
They had earlier in the day pushed Australia into second place, with India in third place, and Canada and Scotland joint fourth.
The women’s 48 kg event was one of two in the weightlifting competition, which was one of many on the first day of competition at the games.
In the other weightlifting event, Nigeria’s Rasaq Tanimowo was in line for a gold medal as he was leading the pack in the competition before the final round of lifts.
The 2014 games, which got underway on Wednesday, will end on 3 August.