Learn Swedish: Ceremonin börjar nu, vad som än må hända ikväll. - The ceremony begins now, whatever may happen tonight.

Historically they share the same root, but they function completely differently today. In this sentence, må is a modal auxiliary verb meaning "may" or "might." It is used to express concession—meaning something will happen regardless of other circumstances. As an auxiliary, it takes an infinitive verb without att (here, hända).

Why do we need som in the phrase vad som än må hända?

In Swedish, when a question word like vad (what) acts as the subject of a subordinate clause, you must add som. Because "whatever" is the thing doing the happening here, it's the subject, making it vad som. If "whatever" were the object of the clause, you wouldn't use som—for example, vad de än må säga (whatever they may say).

What exactly does än do in this sentence?

It provides the "-ever" in "whatever". Pairing a question word with än creates an indefinite meaning. You will see this pattern often: vad... än (whatever), vem... än (whoever), and var... än (wherever).

Could I just say vad som än händer ikväll without using må?