What Metals Stick to a Magnet? The Shop-Floor Answer for Engineers

The metals that stick to a magnet are iron, cobalt, nickel, and the alloys built around them; that short list answers most sorting questions. Aluminum, copper, brass, bronze, and titanium fall on the non-magnetic side, regardless of what a catalog page says. Stainless steel complicates the picture because it is not one magnetic state: annealed austenitic grades such as 18/10 are usually non-magnetic, while ferritic and martensitic grades like 430 attract a magnet, and cold working can make even a nominally austenitic part weakly magnetic. Low-alloy steels such as 4340 stay magnetic because they keep a ferritic matrix. The real test is not whether the metal contains iron—austenitic stainless is mostly iron, yet 18/10 typically does not stick—but whether its microstructure allows magnetic domains to align. When you hold a magnet, start with the alloy family, then confirm the structure before you trust the name.

The Straight Answer: Iron, Cobalt, Nickel, and Their Alloys

Here is the direct answer: iron, cobalt, nickel, and the alloys built around them are the only common metals that stick to a magnet; that short list answers most sorting questions. Aluminum, copper, brass, bronze, and titanium fall on the non-magnetic side no matter what a catalog page claims. Stainless steel muddies the picture because it is not one magnetic state: annealed austenitic grades such as 18/10 are usually non-magnetic, ferritic and martensitic grades like 430 attract a magnet, and cold working can make even a nominally austenitic part weakly magnetic. Low-alloy steels such as 4340 stay magnetic because they keep a ferritic matrix. The real test is not whether the metal contains iron—austenitic stainless is mostly iron, yet 18/10 typically does not stick—but whether its microstructure allows magnetic domains to align. So if a magnet is your tool, start with the alloy family, then confirm the structure before you trust the name.

Picture the moment a magnetic pickup tool lifts more than dropped fasteners: a 'stainless' bracket rides up with them, and the order says it was bought for a non-magnetic electronics enclosure. Open Speedy Metals' July news page and you will see the class of stock that behaves predictably: 4340 alloy round is promoted as a new arrival at a discount if you call, beside turned, ground, and polished bars. 4340 is a low-alloy steel built on iron, so its ferritic structure makes a magnet clamp on without debate; the supplier treats it as ordinary magnetic stock, not a specialty grade. That contrast reshapes how you read any source: a steel name alone does not tell you magnetic behavior; the alloy family and condition do. A catalog listing cannot protect a sensitive assembly; test the bare bar before you trust the label.

Why the Big Three Align: Magnetic Domains Explained

Magnetic attraction is a collective effect. Inside iron, cobalt, and nickel, atoms form magnetic domains, and in an unmagnetized bar those domains point in random directions and cancel out. Bring a magnet close and the domains rotate into alignment, so the metal feels an attraction. Aluminum, copper, brass, and bronze lack this cooperative electron structure; their electrons pair up in a way that prevents domains from forming, which is why a block of 6061 aluminum or a C11000 bushing stays quiet under a magnet. The magnetic list is short because only elements whose atoms can organize into domains produce a useful pull. Heavy metal content alone does not make a part magnetic.

This behavior is not permanent. Each ferromagnetic metal has a Curie temperature; heat scrambles the domains, and even iron becomes non-magnetic above it. Alloying also shifts the outcome. Pure iron attracts a magnet, but combine it with enough nickel and chromium and you get austenite, a face-centered cubic structure that does not support magnetic domains. Cobalt and nickel act like iron on their own, but in an alloy their contribution depends on the crystal phase. For an unknown bar, the right question is not whether it contains iron but what its microstructure is.

The Stainless Exception: 18/10 vs 430 and the Cold-Work Trap

A kitchen pan cracks the stainless myth. A published week-long test of the All-Clad D3 12-inch skillet describes a 3-ply build with 18/10 stainless outside and on the cooking surface around a pure aluminum core—exactly the chemistry people expect to be non-magnetic. The same review says the skillet is induction compatible, meaning part of the structure responds to a magnet. Both facts hold because the 18/10 shell was deeply drawn and spun during manufacturing, which converts some austenite to martensite. That weak magnetism is enough for an induction hob to notice. The procurement lesson: a grade name like 18/10 does not guarantee non-magnetic behavior after forming, so processing history belongs in the specification.

Stainless families split by structure. Ferritic grades such as 430 have a body-centered cubic structure that supports magnetic domains, so they attract a magnet in nearly every condition. Martensitic grades such as 410 and 420 are also magnetic because their hardened structure is an iron lattice. Austenitic grades like 304, 316, and 18/10 are the ones sold as non-magnetic, and that is true only in the annealed state. Cold work converts some austenite to martensite and makes the part pull. The trustworthy sentence is: it is 18/10, it is annealed, and it has not been heavily worked.

Magnetic vs Non-Magnetic Metals: A Shop-Floor Reference

Keep a two-column table near the bench. Magnetic: low-carbon steel, 4340 alloy steel, ferritic stainless such as 430, martensitic stainless such as 410, and most tool steels. Non-magnetic: aluminum alloys such as 1050, 3003, 5052, and 6061; copper alloys such as C11000, C36000 brass, and C93200 bronze; and titanium. An HMaking machining guide summarizes the copper family: C11000 is the best conductor, C36000 is the high-speed machining brass, and C93200 is the wear-resistant bronze. A separate brass-versus-bronze guide makes the same distinction for manufacturing choices: brass is easier to machine, while bronze is the choice for wear, seawater, and load. Neither family carries magnetic domains, but they demand different design decisions, so the non-magnetic column still needs specific alloy numbers.

A supplier catalog can teach the same table. An aluminum category guide lists sheet, plate, and coil in 1050, 1060, 1350, 1070, 3003, 5052, and 6061, from 0.2 mm to 6.0 mm; none of them will hold a magnet. The same Speedy Metals page that sells 4340 alloy round also carries those aluminum products, so magnetic steel and non-magnetic sheet can arrive in one crate. Let the designation lead: 1xxx through 6xxx aluminum stays non-magnetic, while 4340 alloy steel is ferromagnetic. The category label matters less than the digit on the certificate.

From Iron-Only Rules to Precision Alloys: How Standards Evolved

Standards for magnetic metals came in layers. Early tables divided iron and steel from everything else, treating magnetism as an iron property. Once nickel and chromium alloys appeared, engineers realized they could change the magnetic answer without changing the look of the metal, and standards began to call out microstructure rather than chemistry. That is why modern tables separate austenitic, ferritic, and martensitic classes and attach a heat-treatment condition to non-magnetic claims. The history matters because it explains why the word stainless by itself carries no magnetic guarantee, and why a grade certificate is part of the specification rather than optional paperwork.

The timeline continues into current research. A 2020 Metals study compared nickel-aluminum-bronze made by wire-arc additive manufacturing with the same alloy cast conventionally, and found the fabrication route changes internal structure and mechanical properties. Bronze usually sits in the non-magnetic column, and that paper focused on strength rather than magnets, but the implication applies: new processes produce new microstructures, and an old alloy name may no longer predict old behavior. A buyer who sees additively manufactured bronze should confirm the alloy family and the process before assuming the magnet test will match cast results.

Testing With a Magnet Without Getting Fooled

Run the magnet test so it does not fool you. File a small area to bare metal; paint, plating, and passivation can mask the true magnetic response. Slide a small neodymium magnet across the surface rather than dropping it, so roughness cannot mimic a hold. Test several spots, especially after bending, stamping, or welding, because processing can change one zone while leaving another non-magnetic. Support thin sheet so the magnet's own pull cannot bend the metal and create a false attraction. Record the result on the receiving report. This procedure turns a quick it-stuck into a documented check the next shift can trust.

When non-magnetic behavior is critical, tie the test to the purchase order. For stainless, specify an austenitic grade such as 304 or 316, require the annealed condition, and put a magnetic permeability limit on the drawing. For a copper alloy, use a machining guide like Zintilon's to separate C36000 brass from C93200 bronze; both stay non-magnetic but serve different loads. The All-Clad skillet is the cautionary object: heavy forming turned a nominally non-magnetic 18/10 surface slightly magnetic, so a single incoming check is not enough. Re-test finished parts after forming and machining, and if a batch fails, quote the required condition back to the supplier.

Final Verdict: Ordering the Right Metal for the Job

The verdict is a purchase-order rule: when magnetic response matters, write the alloy family, the condition, and the magnet-test or permeability requirement into the spec. Speedy Metals sells 4340 round as everyday magnetic stock with no warning label, because everyone assumes low-alloy steel sticks. The danger comes when someone says stainless for a non-magnetic electronics enclosure. You cannot order by the word steel, and not even by the word stainless. You order an annealed austenitic grade, a copper or aluminum alloy, or another confirmed non-magnetic material, and you verify it on the shop floor before shipment.

Back to the opening: the pickup tool lifted a bracket stamped stainless out of the fastener spill, but that bracket belonged in a non-magnetic enclosure. The label never told you enough; it could be 430, 410, cold-worked 304, or mislabeled steel. The fix is procedural: check the certificate, abrade a clean spot, test the base metal, and if it sticks, return it with a note quoting the annealed condition. Iron, cobalt, nickel, and their alloys stick; aluminum, copper, brass, and bronze do not; stainless is a microstructure question. That rule belongs on the next purchase order.

Iron, cobalt, nickel, and their alloys stick; aluminum, copper, brass, and bronze do not; stainless is a microstructure question—so put the grade, condition, and a shop-floor magnet check on the order before the part ships.