I don’t know why everyone is suggesting complicated means to destroy the steel plate. Acid is expensive and hard to come by and how will you melt it at 3000C in your home?
All you need to do is take a drill and make a few holes in it and you are done. If the drill breaks it means you got a cheap bit. Buy one of those $5 bits and it will drill thru steel like butter pretty much.
You also don’t need to drill all the way, just enough to destroy what is written on the main surface.
This may be a good option but it depends on if you have the machine tools to accomplish this. If you don't have the tools, then there will be the problem of trusting the person that will get this done. If the person is dubious, on the process of getting this done, your keys can be memorized and your funds put in danger. I will still go with the option of @Zaguru12.
The simplest option is transferring the coins on that wallet seed phrase to a new wallet, this way even if the seed phrase is detected it will be useless to the person in its possession.
The steel plate can just be kept at home since steel itself is something of value and there will be no worry if anyone lay hands on it or not because the funds have been moved to another wallet.