It should be fine for most plants, although if you're trying to grow edible fruit in them you might want to line the bucket with some sort of coating, say, varnish (oh, the irony!) or just a plastic bag.
Be careful with the drainage of your soil, as leaving plants soaking in water for several days will probably damage their root systems due to mold and all that, so ensure that you have drainage holes that don't go anywhere that water might be destructive.