[424B5] Momentus Inc. Prospectus Supplement (Debt Securities)

Rhea-AI Filing Summary

Momentus Inc. (MNTS) filed a prospectus supplement updating its at-the-market (ATM) program capacity. The company may offer and sell shares of Class A common stock with an aggregate offering price of up to $3,812,914.01 under General Instruction I.B.6 of Form S‑3, through A.G.P./Alliance Global Partners as sales agent or principal.

This update reflects the one‑third public float limit. The public float used for the cap was $38,990,626.56, calculated from 22,801,536 non‑affiliate shares at $1.71 per share, the highest closing price within the prior 60 days. The company has already sold $9,183,961.51 over the last 12 months under I.B.6; the new capacity does not include those prior sales. If the public float rises, the company may file another supplement to increase available ATM capacity, and the I.B.6 limit falls away once float exceeds $75.0 million. MNTS last traded at $1.33 on October 17, 2025.

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Capital markets strategist

Neutral update: MNTS refreshes ATM capacity to $3.81M under I.B.6.

The filing updates the company’s at‑the‑market equity program, allowing sales of up to $3,812,914.01 of common stock through A.G.P., subject to Form S‑3 General Instruction I.B.6. The cap reflects one‑third of the stated public float calculation.

The float is listed as $38,990,626.56, derived from 22,801,536 non‑affiliate shares at $1.71 as of October 14, 2025. The company notes $9,183,961.51 sold over the prior 12 months, which informs the remaining capacity.

Actual issuance depends on company decisions and market conditions. If float exceeds $75.0 million, I.B.6 limits fall away; subsequent filings may provide additional capacity details.

Filed Pursuant to Rule 424(b)(5)

Registration No. 333- 290425

PROSPECTUS SUPPLEMENT

(To Prospectus Supplement dated October 10, 2025)

(To Prospectus and Prospectus Supplement dated September 30, 2025)

Up to $3,812,914.01

of Common Stock

This prospectus supplement (the “Prospectus Supplement”) amends and supplements the prospectus supplement dated October 10, 2025, the prospectus supplement dated September 30, 2025 and the accompanying base prospectus dated September 30, 2025 filed with the Securities and exchange Commission as part of our registration statement on Form S-3 (collectively, the “ATM Prospectus”), relating to the offer and sale of shares of our Class A common stock, par value $0.00001 per share (“common stock”) from time to time pursuant to the terms of the sales agreement dated September 19, 2025 (the “ATM Agreement”) with A.G.P./Alliance Global Partners (the “Sales Agent”), acting as our sales agent or principal. This Prospectus Supplement should be read in conjunction with the ATM Prospectus, and is qualified by reference thereto, except to the extent that the information herein amends or supersedes the information contained in the ATM Prospectus. This Prospectus Supplement is not complete without and may only be delivered or utilized in connection with the ATM Prospectus, and any future amendments or supplements thereto.

We are subject to the offering limits in General Instruction I.B.6 of Form S-3. As of the date of this Prospectus Supplement, the aggregate market value of our common stock held by non-affiliates pursuant to General Instruction I.B.6 of Form S-3 is $38,990,626.56, which was calculated based on 22,801,536 shares of our outstanding common stock held by non-affiliates and a price of $1.71 per share, the closing price of our common stock on October 14, 2025, which is the highest closing sale price of our common stock on the Nasdaq Capital Market (“Nasdaq”) within the prior 60 days. As of the date of this Prospectus Supplement, we have sold an aggregate of $9,183,961.51 of shares of our common stock pursuant to General Instruction I.B.6 of Form S-3 during the 12 calendar months prior to, and including, the date of this Prospectus Supplement. As such, $3,812,914.01 is available to be sold pursuant to this Prospectus Supplement. Pursuant to General Instruction I.B.6 of Form S-3, in no event will we sell securities in public primary offerings on Form S-3 with a value exceeding one-third of our public float (as defined by General Instruction I.B.6) in any twelve calendar month period so long as our public float remains below $75.0 million.

We are filing this Prospectus Supplement to amend the ATM Prospectus to update the maximum amount of shares that we are eligible to sell under General Instruction I.B.6. As a result of these limitations, we may offer and sell shares of our common stock having an aggregate offering price of up to $3,812,914.01 (which does not include the $9,183,961.51 of shares previously sold under the ATM Agreement) pursuant to this Prospectus Supplement in accordance with the terms of the ATM Agreement. However, in the event that our public float increases, we may sell additional securities in public primary offerings on Form S-3 with a value up to one-third of our public float, in each case calculated pursuant to General Instruction I.B.6 and subject to the terms of the Agreement. In the event that our public float increases above $75.0 million, we will no longer be subject to the limits in General Instruction I.B.6 of Form S-3. If our public float increases such that we may sell additional amounts under the ATM Agreement and the registration statement of which this Prospectus Supplement and the ATM Prospectus are a part, we will file another prospectus supplement prior to making additional sales.

Our common stock is listed on Nasdaq under the symbol “MNTS.” On October 17, 2025, the last reported sale price of our common stock on Nasdaq was $1.33 per share.

Investing in our common stock involves a high degree of risk. Before making an investment decision, please read the information under the heading “Risk Factors” beginning on page S-12 of the ATM Prospectus and in the documents incorporated by reference into this prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

A.G.P.

The date of this prospectus supplement is October 20, 2025

FAQ

What did MNTS update in its 424B5 filing?

MNTS updated its ATM program capacity to allow sales of up to $3,812,914.01 of common stock under General Instruction I.B.6 of Form S‑3.

How was Momentus’s public float calculated for this update?

Public float was $38,990,626.56, based on 22,801,536 non‑affiliate shares at $1.71 per share, the highest closing price in the prior 60 days.

How much has MNTS already sold under I.B.6 in the past 12 months?

The company has sold an aggregate of $9,183,961.51 of common stock during the last 12 months under I.B.6.

What happens if MNTS’s public float exceeds $75.0 million?

If public float exceeds $75.0 million, the I.B.6 limitations no longer apply.

Who is the sales agent for the ATM program?

A.G.P./Alliance Global Partners acts as the sales agent or principal under the ATM Agreement.

What is MNTS’s recent stock price reference in the filing?

The last reported sale price on Nasdaq was $1.33 per share on October 17, 2025.