If this is your first experience then consider using the world generator[valheim-map.world] to at least convince yourself that what folks here are trying to tell you is indeed true. There should be plenty of crypts in multiple swamp locations to supply iron to at least get through the 3rd boss. After he drops the wishbone, you can use that to locate even more iron in swamps that don't have crypts but still have muddy scrap piles buried in small hills. By the time you reach Mistlands you will find plenty of iron in either Jotun armor sites or in rebar used in marble construction. You are accurate in assessing iron as perhaps the most used resource in the game next to stone and wood.