In Mistborn books one and two (and likely others, haven't read more than the first part of the second one so far), there are symbols at the beginnings of all the chapters. They resemble the ones in the corners of the map. What are these symbols?
That's the steel alphabet used on Scadrial.
Since you haven't finished the series, I'd be careful of spoilers, but each symbol is a glyph, but each also represents a different metal. For example, the one in the very top left of the picture in your question represents steel.
The accepted answer is good, but I learned something recently that's pretty cool: they represent numbers, not just sounds.
At the beginning of each chapter there is the chapter number in our normal base 10 Arabic numerals at the top, and one or two steel alphabet symbols representing the chapter number. That is why there are so many of them in the books.
Iron is 1, steel is 2, tin is 3, pewter is 4, zinc is 5, and so on. There is a special character just for 0 with no corresponding metal or letter, and many characters that don't have a corresponding metal due to needing more than 16 letters.
Because it is hexadecimal, 10 (bendalloy) through 15 (aluminum) are still just one symbol each, and 16 would be written as the symbol for a 1 and the symbol for a 0.
List of symbols' number meanings from here.