Shareholder Vote · Company Update

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549   FORM 8-K   CURRENT REPORT   Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 7, 2026 MUELLER INDUSTRIES INC . (Exact name of registrant as specified in its charter)   Delaware 1-6770 25-0790410 (State or other jurisdiction (Commission File (IRS Employer of incorporation) Number) Identification No.)    150 Schilling Boulevard Suite 100 Collierville Tennessee 38017 (Address of principal executive offices) (Zip Code) Registrant’s telephone number, including area code: (901) 753-3200 Registrant’s Former Name or Address, if changed since last report: N/A   Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)  ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)  ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))  ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))  Securities registered pursuant to Section 12(b) of the Act: Title of each class Trading Symbol Name of exchange on which registered Common Stock, $0.01 Par Value MLI NYSE    Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new of revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ Item 5.07 Submission of Matters to a Vote of Security Holders. On May 7, 2026, the Company held its Annual Meeting of Stockholders, at which three proposals were voted upon. The results of the vote are as follows: Proposal 1 - Election of directors; the following persons were duly elected to serve, subject to the Company’s By-laws, as Directors of the Company until the next Annual Meeting, or until election and qualification of their successors: For Withheld Gregory L. Christopher 91,402,399 2,458,354 Elizabeth Donovan 64,132,441 29,728,312 William C. Drummond 92,784,657 1,076,096 Gary S. Gladstein 90,662,750 3,198,003 Scott J. Goldman 91,787,157 2,073,596 John B. Hansen 91,545,665 2,315,088 Terry Hermanson 87,392,647 6,468,106 Charles P. Herzog, Jr. 88,535,358 5,325,395 Proposal 2 - The Company’s stockholders approved the appointment of Ernst & Young LLP as the Company’s independent auditors for the fiscal year ending December 26, 2026: For Against Abstain 98,482,822 2,465,822 316,383 Proposal 3 - The Company’s stockholders approved an advisory vote on the compensation of the Company’s named executive officers: For Against Abstain Broker Non-Votes 87,587,873 4,306,124 1,966,756 7,404,274 Item 8.01 Other Events. On May 8, 2026 the Registrant issued a press release announcing that its Board has declared a regular quarterly cash dividend of 35 cents per share on its common stock.  The dividend will be paid June 19, 2026 to shareholders of record on June 5, 2026.  A copy of the press release announcing the payment and record dates is attached as Exhibit 99.1. Item 9.01 Financial Statements and Exhibits.   (d) Exhibits   99.1 Press release, dated May 8, 2026 2 SIGNATURES   Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the Registrant has duly caused this Report to be signed on its behalf by the undersigned hereunto duly authorized.   MUELLER INDUSTRIES, INC. By: /s/ ANTHONY J. STEINRIEDE Name: Anthony J. Steinriede Title: Vice President - Corporate Controller Date: May 11, 2026 3