Meta-Alloys are a special commodity in-game that can be used to unlock certain engineers, special modules and even fed to Thargoids. Here are a few different methods to collect Meta-Alloys.
Despite what some people say, Meta-Alloys are NOT CAUSTIC and will NOT deal damage to your ship if you carry them around. However, if you are scanned by a Thargoid Interceptor while carrying them, they may make some different noises, but ultimately they will not attack you.
Barnacles are the most common method to gathering Meta-Alloys, these can be found in 4 different regions of space.
The Pleiades Nebula
The Witch Head Nebula
The California Nebula
The Coalsack Nebula
Thargoid Barnacles are planetary surface sites that can be used to gather Meta-Alloys by shooting down the Large spikes that grow at these.
It is possible that these sites can be depleted so you must make sure that you are visiting a site that is NOT depleted when looking for one.
Here is a link to CMDR Panpipers barnacle spreadsheet, this can be used to find ripe barnacles and also sites that can be used to gather materials too.
Once you find a Meta-Alloy spike, you can break it and re-log the game to make it spawn another Meta-Alloy.
In the area surrounding Thargoid Surface Structures you can often find 2-3 barnacle spikes containing Meta-Alloys. These can be broken for a constant supply of Alloys and also do not deplete.
Non-Human Signal Sources
When dropping into a Non-Human Signal Source [Threat 5-7] there is a small chance a Meta-Alloy can be found floating in the instance. Beware, if any Thargoid Interceptors are present, they may try to collect it before you get a chance to scoop it up.
You can visit a Thargoid Barnacle Forest. Barnacle Forests are special barnacle sites with many barnacles, unlike normal barnacles, these do not deplete and will always have fresh ripe barnacles available.
A few well known forest sites:
Hyades Sector AQ-Y d81 C 2 at 9.2924, -153.9815