Which Metals Are Magnetic, and Why It Matters

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Which Metals Are Magnetic – and Why?: Which metals are magnetic comes down to one element more than any other: iron. If something sticks to a magnet, iron is almost always doing the work, either as the metal itself or as the dominant ingredient in an alloy like steel. Nickel and cobalt are magnetic too, but neither turns up often in general construction or engineering. Everything else people usually ask about, aluminium, copper, brass, zinc, lead, and most stainless steel, won't hold a magnetic field at all. What metals are magnetic gets more interesting once you get to steel specifically, because "steel" isn't one material: some grades are strongly magnetic, some barely respond, and a few change behaviour depending on how they've been worked.

Why Are Some Metals Magnetic and Others Aren't?

Magnetism comes down to how a metal's atoms are arranged, and specifically how their electrons behave. In a small group of metals, iron chief among them, neighbouring atoms line their magnetic fields up with each other across small regions called magnetic domains. Bring the metal close to a magnet, or apply an external field, and those domains snap into alignment, creating a strong, easily felt pull. This is ferromagnetism, and it's the only form of magnetism strong enough to matter on a building site or in a fabrication shop.

Most other metals are either paramagnetic, weakly and almost imperceptibly drawn to a magnet, or diamagnetic, very slightly repelled. Aluminium and platinum are paramagnetic; copper, silver, gold and zinc are diamagnetic. In practical terms, both behave as non-magnetic, since the effect is far too small to notice without laboratory equipment. Crystal structure plays a role too: iron's magnetism depends on it holding a body-centred cubic structure at room temperature, which is exactly the structure ordinary carbon steel keeps. Change that structure, through alloying or heat treatment, and the magnetic behaviour can change with it.

This is closely related to, but not quite the same as, the ferrous and non-ferrous distinction: ferrous metals contain iron and are usually, though not always, magnetic, while non-ferrous metals don't and aren't. For more on that, see our guide to ferrous vs non-ferrous metals.

The Metals That Are Magnetic

Only three metals are ferromagnetic at room temperature in their pure form: iron, nickel and cobalt. Gadolinium, a rare-earth metal, is also ferromagnetic, but only just below room temperature, and it's rarely encountered outside specialist scientific and medical equipment. For anyone buying, specifying or fabricating metal day to day, iron is the one that matters, not because nickel and cobalt aren't magnetic, but because iron is by far the most abundant of the three and forms the basis of every carbon and mild steel product on the market. Even the strongest permanent magnets made, neodymium magnets, aren't a rare-earth metal working alone; they're an alloy of iron with neodymium and boron, with iron doing much of the magnetic work.

Is Steel Magnetic?

For ordinary carbon and mild steel, the S275 and S355 grades used in universal beams, columns, hollow sections and bar, yes, and strongly so. Steel is fundamentally iron with a small percentage of carbon added for strength, and that iron content keeps its ferritic, body-centred cubic structure at room temperature, which is what gives it a firm, unmistakable pull toward a magnet.

It's worth separating magnetism from rust resistance, since the two get conflated on site. Magnetism is about crystal structure, not surface chemistry, so it has nothing to do with whether a metal corrodes. A galvanised steel beam is exactly as magnetic as an untreated one, because the zinc coating changes how the steel weathers, not what it's attracted to.

Stainless Steel and Magnetism: Why Grade Changes Everything

This is where the simple "iron is magnetic" rule runs into its biggest exception, and it's a common point of confusion on site. Stainless steel is still mostly iron, typically 70% or more, but adding enough chromium and nickel changes its crystal structure from the ferritic form found in mild steel to an austenitic structure, which isn't ferromagnetic. According to the British Stainless Steel Association, fully austenitic stainless steel has a magnetic permeability of around 1.0, next to no different from air, compared with a figure of at least 200 for ordinary mild or carbon steel.

The two stainless grades BM Steel stocks in its stainless steel handrail tube range, 304 and 316, are both austenitic, and in their standard, annealed condition, neither is meaningfully magnetic. That's not a coincidence: the same structure that suppresses magnetism also gives these grades their corrosion resistance, which is why 316 in particular gets specified for coastal and exposed environments.

There's a genuine complication worth flagging, though. Cold working, bending, rolling, or heavily forming a component, can transform some of that austenite into martensite, a structure that is ferromagnetic. A cold-formed edge or a tightly bent piece of 304 tube can pick up a noticeably stronger pull than the flat, unworked section right next to it, even though the material specification hasn't changed. Not every stainless steel behaves this way, either. Ferritic grades, such as 430, and martensitic grades, such as 410 and 420, are magnetic from the outset by design, regardless of how they've been worked. Duplex stainless steels, which mix austenitic and ferritic structures, sit magnetically somewhere in between.

Magnetic vs Non-Magnetic Metals at a Glance

If you're trying to place a specific component, start with what you already know. A mild or carbon steel structural section is already confirmed magnetic, and a component marked 304 or 316 that hasn't been bent, formed or welded should show little to no pull. It's the in-between cases, cold-worked stainless, an unmarked offcut, a mixed batch, where a quick magnet test earns its keep as a first check, backed up by a mill certificate wherever the answer genuinely matters.

Here's how the metals covered above compare side by side.

Metal / Alloy	Magnetic?	Why
Mild and carbon steel (S275, S355)	Yes, strongly	Ferritic, iron-based structure
Cast iron	Yes	High iron content, ferritic/pearlitic structure
Ferritic stainless steel (e.g. 430)	Yes	Retains a ferritic structure despite alloying
Martensitic stainless steel (e.g. 410, 420)	Yes	Martensitic structure is ferromagnetic
Duplex stainless steel	Weakly	Mixed austenite/ferrite structure
Austenitic stainless steel (304, 316), annealed	No, or negligible	Austenite isn't ferromagnetic
Nickel, cobalt (pure)	Yes	Ferromagnetic elements
Aluminium	No	Paramagnetic, too weak to detect by hand
Copper, brass, zinc, lead	No	Diamagnetic

Why Magnetism Matters When Specifying or Fabricating

Beyond curiosity, magnetism has a few genuinely practical uses worth knowing about. A magnet is a fast, if imperfect, way to sanity-check what you're holding. If a component that's supposed to be aluminium sticks firmly, something's wrong with the order. If a "stainless" fitting pulls hard, it may be a cheaper ferritic or martensitic grade rather than the austenitic 304 or 316 that was specified, worth knowing before it goes into a marine or food-contact application where the wrong grade will corrode. Treat it as a rule of thumb rather than proof, though: as covered above, cold-worked 304 can develop a weak magnetic pull of its own, so a mill certificate is still the only way to be certain of grade.

Magnetism also decides how a weld gets inspected. Magnetic particle inspection is a standard non-destructive testing method for finding surface and near-surface cracks in a weld, but it only works on ferromagnetic material: mild steel, and ferritic or martensitic stainless. For austenitic stainless steel, aluminium, or anything else non-magnetic, dye penetrant testing does the same job instead, since there's no magnetic field for particle inspection to disturb. Knowing which grade you're welding, in other words, decides which inspection method applies.

At the other end of a project's life, magnetism is also how scrap yards separate ferrous steel from non-ferrous metals at speed, using overhead magnets to pull mild steel and cast iron out of a mixed load before it's baled or shredded.

BM Steel's Structural, Engineering and Stainless Steel Range

Whatever the application, grade is worth confirming before you order rather than after. BM Steel stocks universal beams, universal columns and other structural sections in standard S275 and S355 carbon steel, all strongly magnetic, available cut to length with free cutting on selected products, alongside engineering steel bar in EN grades for machined and stressed components. For architectural and balustrade work where a non-magnetic, corrosion-resistant finish matters, our stainless steel handrail tube range covers grade 304 for internal use and grade 316 for coastal or exposed applications. And where a magnetic base metal needs to go outdoors without rusting, our galvanised sheet range does the job without changing what the steel underneath is attracted to.

Universal Beams

Universal Columns

Engineering Steel

Sheets & Plates

Round Handrails

Square Handrails

FAQs about Metal Magnetism

Can a magnet test tell you what steel or stainless steel grade you have?

Not on its own. A strong pull points toward mild steel or a ferritic or martensitic stainless grade; little or no response points toward an austenitic grade like 304 or 316. It isn't conclusive, though: cold-worked austenitic stainless can develop a weak magnetic pull without the grade actually changing, and some ferritic grades resist a magnet strongly enough to be mistaken for mild steel. Where grade genuinely matters, structural calculations, food-contact equipment, marine fittings, a mill certificate or supplier record is the only reliable confirmation.

Does galvanising change whether steel is magnetic?

No. Galvanising adds a zinc coating to the surface of the steel; it doesn't touch the iron-carbon structure underneath, which is what determines magnetism. A galvanised beam or sheet pulls to a magnet exactly the same way as the same section left untreated. The coating changes corrosion resistance, not what the base metal is attracted to.

Why isn't aluminium magnetic, even though it's a metal?

Aluminium has no unpaired electrons arranging themselves into the aligned domains that ferromagnetism needs, so it's classed as paramagnetic instead: it responds to a magnetic field, but so weakly that the effect is undetectable without sensitive lab equipment. That's true of most non-ferrous metals; copper, brass, zinc and lead behave the same way, just in the opposite, diamagnetic, direction.

Can welding change how magnetic a stainless steel component is?

Yes, and it's a genuine consideration for fabricators. Welding austenitic stainless steel briefly heats the metal enough to shift some of the structure toward ferrite, and filler wires are often formulated with a deliberate small percentage of ferrite to reduce the risk of cracking during welding. The result is that a weld and its surrounding heat-affected zone can be measurably more magnetic than the parent material either side of it, even though both are nominally the same grade.

Posted by Craig Silvain
19th August 2026

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