Generally yes but even this won't cover you fully.
The resistance between the case and the earth conductor should be under 0.1Ohms. The minimum resistance between live, neutral and earth should be >1MOhm with a leakage current of no more than 1mA.
The earth connection should also be made with a shake proof washer so it doesn't become disconnected.
However there are ways to design a product so the case doesn't need to be earthed which can achieved by insulating all of the mains conductors with reinforced or double insulation, so no single fault can cause the case to be live. If you don't understand this then always earth the case.