This wire food dome will keep flies off your food. However, if flies are a persistent pest, you might like to consider the following tips:

1. Keep your house as clean as possible. Flies love any spilt food, crumbs or dead insects so wipe surfaces and vacuum as often as possible.
2. Empty your bins every day. Its tempting to wait until they are brimming over, we've all done it, but in the summer months this will attract flies.
3. Keep a fly swatter handy. You're never going to get them all, but at least you will have some satisfaction for killing a few.