You're on glue means and refers to the desperation of an individual's actions or words, accusing them of becoming intoxicated on the poorest of substances, or in other words, doing anything to further themselves from sober, logical thinking by way of intentional self delusion.
To be stuck on an illogical conclusion, or belief system, to such an extent that a person is literally, and purposefully deluding themselves by way of substance abuse.
Someone who is "on glue" isn't just using a drug.
It means that they are desperate, and usually in a very bad time in their life.
Glue still means "adhesive", but some people will do what's called "huffing", where they inhale fumes from chemicals to get high.
Glue is a commonly used substance.
It is VERY dangerous and bad for you.
People who do it are usually very confused or depressed mentally, which is why saying, "am I on glue?" means, "am I crazy?"
The saying "am I on glue?" can be considered sarcastic or even impolite, so be careful how you use it.
There's also another saying with glue.
Kids typically use a type of insult which says I'm rubber you're glue whatever you have to say bounces off of me and sticks to you.
means the insult said by the first child doesn't apply to the person being insulted, but the person who said it in the first place. You look ugly. I'm rubber you're glue.