Long-running excavations at the ‘central place’ of Helgö in Lake Mälaren uncovered an unprecedented range of primary metal alloys, mainly in association with a Migration-period workshop. Since primary metals are extremely rare in Migration-period contexts, the source(s) of these metals is a central question with the potential to yield new insights into resource acquisition, international contacts and supply and exchange networks in fifth- to early sixth-century Sweden. Using a combination of lead isotope and trace element analyses, we assess the provenance of 19 artefacts of lead, copper and brass, including ingots, rods and casting waste. While the origin of the copper could not be determined with certainty, the results of the brass and lead were intriguing. Three lead melts stem from Swedish leadore, and represent the earliest direct archaeological evidence for lead extraction in Sweden. By contrast, the brass was imported over long distances. We propose that it reached Helgö as part of a routinized trade with the Byzantine Empire, potentially the eastern Mediterranean region, with one ingot having probable origins in Asia. The results thus indicate both the local exploitation of available ores and far-reaching contacts, which may have extended as far as the Silk Road.