Major BABYMETAL concerts can get rather extravagant, with complex stages and lots of video. It is common for the primary platform to have a video screen for a floor. In the graphics displayed on the floor at the Budokan shows in 2021, there is a typo in the displayed lyrics for BxMxC.
In Romaji, the line is "Tekina metaru saifaa". There are a few different translations for tekina, but it is generally accepted that metal cypher refers to the freestyle rap format, with a metal flavor. It is displayed in a mix of Hiragana and Katakana:
てきな メタルサイファー
On the main video screens, the graphics look like this example from the Legend Metal Galaxy show.
On the floor graphics, there is a case when the text is shown as "Tekina metaru safiaa":
てきな メタルサフィアー
It is a mix of characters with the same shapes, but in a different sequence, and also a different character is slightly smaller, to be part of the extended Katakana for either FA or FI. This image comes from KuroKitsuneSama's video, at 2:35. The image is squashed a little to un-distort the characters to make them more readable. And they are doubled up for an effect, where the first instance is displayed immediately, and the second sequence is displayed progressively to match the audio.
Later, a different graphic for this line shows the correct SA I FAA spelling.
Google Translate gave me "metal sapphire" as the translation of メタルサフィア. But sapphire in English is shown as サファイア, SA FA I A. So, the typo SA FI A is not the best transcription of sapphire in Katakana. But "metal sapphire" seemed like a cool thing, and the domain was available, so here we are.
SA FI A could be written as Sapphia, which is a name that shows up in many places. Sapphia's Table is a location in some Legend of Zelda games. If the spelling was not a simple accident, it's not clear what the graphics designer was intending.