useless elements are useless
gallium can break alluminium(not in the game)
BREL is aluminium in tpt.
brel is strange - exotic aluminum because it can cerate exot
Even if there's only one indication that BREL is aluminum, it's still an indication.
But all of BREL's other properties aren't indications that BREL isn't aluminum, ergo BREL's reaction with BRMT confirms that BREL is aluminium. It's true that aluminium melts in real life, but tpt isn't meant to by completely realistic; for example, the biggest inaccuracy in tpt is PSCN conducting to NSCN but not vice-versa; it's one of the most widely-used properties in tpt, but in real life, the other way around is the case.
Technically, thermites can be made with any metal and a metal oxide with reactivity lower than the metal, so BREL could theoretically be potassium or titanium or basically any metal above iron in this list https://en.wikipedia.org/wiki/Reactivity_series