I am everywhere
I am weightless
You can see me.
If you put me in a Bucket,
Bucket gets lighter.
Who am I?
Are you
a hole?
I am everywhere
This probably either refers to holes all around us, e.g., keyholes, or anywhere we have air, i.e., not a solid object.
I am weightless
A hole means lack of substance, so no weight.
You can see me.
You can see the hole due to the fact you can see through it.
If you put me in a Bucket, Bucket gets lighter.
Putting holes in a bucket removes material and makes it lighter.
You could be
light
...beause...
Light is found everywhere (all matter at temperature above absolute zero emits thermal electromagnetic radiation) Photons have zero mass (weightless) You can see light (depending on frequency of course) And if you 'put' light in a bucket (shine a torch on it, add a candle, etc), the interior of the bucket is less dark, i.e. lighter.
clouds
they are weightless but existed but can not an are weightless till they shift form into drops from the water vapors that forms them.